1/25/2018

1

Bio 1101 Lec. 5, Part A Chapter 6: Cellular Respiration

•

•

•

–

•

• Energy is needed by cells to do work

– Chemical energy, a form of potential energy, is stored in bonds of food molecules (such as glucose)

– Energy from food is transferred in cellular respiration to high-energy ATP molecules, which allow the cell to do work

•

•

Cellular Respiration

•

• Multi-step chemical process (metabolic pathway)

• 2 of the 3 steps occur within the mitochondria; the first step occurs outside of the

mitochondria, in the cytoplasm

• Both plant and animal cells use cellular respiration to obtain energy from food molecules

• Reaction occurs in the presence of oxygen

C6H12O6 + 6O2 6CO2 + 6H2O + ATPs (energy)

•

C6H12O6 + 6O2 6CO2 + 6H2O + ATPs (energy)

• In Cellular Respiration, hydrogens are removed from sugar and transferred to oxygen

– Including their electrons

• Redox Reactions (aka Oxidation-Reduction Reactions) involve the transfer of electrons from

one substance to another

– Cellular respiration is therefore a redox reaction

– Electrons (hydrogens) move from glucose to oxygen

–

•

C6H12O6 + 6O2 6CO2 + 6H2O + ATPs (energy)

• In a Redox Reaction:

– The molecule that loses an electron is said to be oxidized

• Glucose is oxidized in cellular respiration

– The molecule that gains electrons is said to be reduced

• Oxygen is reduced in cellular respiration

– Energy is generated because electrons “fall” from a level of higher energy to lower

energy

• The oxygen has a greater affinity for the hydrogen electrons than did the glucose molecule

•

• How do the electrons get to oxygen?

– Via the electron acceptor NAD+

– (Nicotinamide Adenine Dinucleotide)

–Made from niacin (vitamin B3)

–When electrons (hydrogens) are transferred from food to NAD+, it becomes reduced to

NADH

– NADH transports the electrons to the Electron Transport Chain, which ultimately carries

them to the final oxygen acceptor

– This is where most of the energy from food is captured to make ATP

•

• The purpose of cellular respiration: to produce ATP’s – the high-energy molecules that do cellular work

• Cellular respiration is efficient and can produce up to approximately 32 ATP’s

• Step 1: Glycolysis

•

• 1 molecule of Glucose is broken down into 2 molecules of pyruvic acid

– Glucose has 6 carbons

– Pyruvic acid has 3 carbons

• A net of 2 ATP molecules are created from ADPs

– Recall, 2 were used to split glucose

– 2 ATPs were then created from each pyruvic acid

• 2 NADH molecules are created from NAD+ molecules (one per molecule of pyruvic acid)

– NADHs carry electrons to the “electron transport chain,” where most of the ATPs are

created

•

• Step 2: Krebs Cycle (aka Citric Acid Cycle)

– But first, pyruvic acid must be converted to acetyl-CoA

• Pyruvic acid from glycolysis is converted into acetic acid – a 2-carbon compound

• In the process, 2 carbon dioxide molecules are given off

• The acetic acid combines with an enzyme called Co-a, making “Acetyl-CoA”

• Acetyl-CoA is the fuel of the Krebs cycle (aka Citric Acid Cycle)

Krebs Cycle (aka Citric Acid Cycle)

• 2 ATPs are generated directly in the Krebs cycle per glucose

• 6 NADHs and 2 FADH2s are also generated, per glucose

– These molecules carry electrons to the electron transport chain

•

• Krebs Cycle Video:

– https://www.youtube.com/watch?v=uF9XYgLDlFI

• Step 3: Electron Transport Chain (ETC)

– The “machinery” of the ETC is built into the membranes of the mitochondria

• That’s why there are so many inner-foldings of membrane in mitochondria

•

• A series of molecules in the mitochondrial membranes accept electrons

• The first molecule in the chain accepts the electron from NADH

• Passes it on to the next molecule, and so on…

• At each step, energy is given up that is used to make ATPs

– About 28 ATPs produced here!

• Finally, the electrons (and the hydrogen) are accepted by oxygen, making water

•

• Electron Transport Chain Video:

•

• http://www.youtube.com/watch?v=xbJ0nbzt5Kw

• How do organisms obtain energy from food when oxygen isn’t available?

•

• Fermentation…

•

•

•

•

• Ancient organisms likely used glycolysis to make ATP

– No oxygen in the early Earth’s atmosphere

– Today, glycolysis occurs in nearly all organisms

–Must be an ancient metabolic pathway

•

•

• Today, with abundant oxygen, most organisms use cellular respiration

• However, a variety of organisms use anaerobic fermentation

– Fermentation is used by some organisms as their primary metabolic pathway (some

bacteria and yeasts)

–Others switch between fermentation and aerobic respiration, depending on availability of

oxygen

•

• In animals, some cells must function for short periods of time without oxygen

– i.e. when exercising strenuously

• Blood supplies your cells with oxygen for cellular respiration

• If you are consuming energy faster than oxygen, your muscle cells may resort to lactic acid

fermentation to obtain energy

• Very similar to glycolysis (first step of cellular respiration – doesn’t require oxygen)

•

• Fermentation

•

• Much less efficient than cellular respiration, however

–Only 2 ATPs produced, compared to 32 for cellular respiration

– Consume more food molecules to obtain the same amount of energy using fermentation

– Also produces lactic acid as a by-product, which accumulates and makes muscles ache

•

–Microbes that use fermentation as metabolic pathway are used in producing

• Cheeses

• Yogurt

• Bread

• Alcohol

• Soy sauce

• Pickled vegetables

– The CO2 produced by yeasts is also what makes bread rise

•

Bonus Activity

• How is burning a marshmallow similar to/ & different from cellular respiration?

•

• Then, we’ll make s’mores

• For an added biology lesson, let’s look at the ingredients in chocolate

• I used to use Nutella instead of regular chocolate squares, to make “gourmet” s’mores,

BUT:

– Recently learned Nutella and many other chocolate products contain Palm Oil

– Palm Oil is most commonly produced by palm plantations growing in tropical areas; tropical rainforest is cut down to grow these plants; orangutans and tigers are two endangered species that are especially threatened by palm oil plantations

– So, now I look for palm-oil free products

– http://www.youtube.com/watch?v=3I-dxfCaQLU

– http://www.youtube.com/watch?v=oRQWj4H9nH0

• 5-minute break…

•

• Next, Photosynthesis

•

•

•

–

•

Photosynthesis

• Plants are photosynthetic autotrophs

– Generate own food from inorganic ingredients

– Process of photosynthesis is essentially the reverse of cellular respiration:

6CO2 + 6H2O energy C6H12O6 + 6O2

(recall cellular respiration: C6H12O6 + 6O2 6CO2 + 6H2O + energy)

•

• Besides plants, many protists (such as algae, seaweed, microscopic protists like Euglena) and bacteria are also photosynthetic

– In bacteria, photosynthesis doesn’t occur in chloroplasts (recall, prokaryotes do not have membrane-bound organelles)

•

• In eukaryotes, photosynthesis occurs in chloroplasts

•

• Chlorophyll is the pigment in chloroplasts that give them their green color, and absorb light

energy from the sun

•

• In plants, leaves are the structures that contain the most chloroplasts

–Mostly in the mesophyll (“the green tissue in the interior of the leaf”)

•

– Chloroplasts are surrounded by a double membrane

– Inside, filled with thick fluid called stroma

– Suspended in that fluid are stacks of disks called thylakoids; a stack of thylakoids is called a granum

– Photosynthetic pigments (such as chlorophyll) are built into the thylakoid membranes

•

• Photosynthesis consists of two, multi-step processes: the light reactions, and the Calvin

cycle

– Light Reactions – use sunlight to build ATP and NADPH

– Calvin Cycle – uses the energy from the light reactions to build sugar

• Although doesn’t need sunlight directly, can’t synthesize sugar without the ATPs generated in the light reactions

• If runs out of ATPs, can’t build more sugars until sunlight is available to begin the light

reactions again

•

•

• How is the energy from sunlight captured by plants?

•

– Sunlight is a type of electromagnetic energy

– Light travels in waves

• Different colors of light have different wavelengths

• There are also wavelengths of light that are outside of the visible spectrum

•

– Pigments are visible as different colors because they reflect certain wavelengths and absorb others

• Example: the feathers of a cardinal look red because the pigment in them reflects light with a red wavelength, and absorbs the other wavelengths of visible light

– Likewise, leaves of plants appear green because chlorophyll reflects green light

•

• So which wavelengths of light are best used by plants to do photosynthesis?

– Not green, because it is reflected

–Other colors, like reds, oranges, blues, and purples can be absorbed

– Study of bacteria growing in water with algae and seeking oxygen…

•

• There are different types of pigments in plants

– Chlorphyll a – reflects green light, and participates directly in the light reactions

– Chlorophyll b – reflects yellow-green light; may participate indirectly in the light reactions

– Carotenoids – reflect yellow/orange/ light; may pass energy to chlorophyll a, or may protect plant cells by absorbing excess light energy

• Many herbicides work by inhibiting synthesis of carotenoids

• Leads to damage of chlorophyll because free radicals (unpaired electrons) build up and damage molecules

• Plants evolved this strategy to protect their chlorophyll; carotenoids can protect our

cells, too (reducing cancer risk, for example)

•

– Fall colors due to decreases in green chlorophyll, making visible the effects of the carotenoids

•

Step 1 of Photosynthesis: The Light Reactions

• The Light Reactions

• Light Reactions in a nutshell

– Light energy (photons) are absorbed by pigments and used to excite electrons in the water-splitting photosystem

– Excited electrons are accepted by molecules in the electron transport chain (built into the membranes of the thylakoids); oxygen is given off as a by-product

– Energy from the ETC is used to make ATPs (same concept as the ETC in cellular

respiration)

– The electrons then pass to the NADPH-producing photosystem, where they are re-

excited by light absorbed by pigment

– The electron is then used to produce NADPH, which is used in the Calvin Cycle

•

• The Calvin Cycle – Where Sugar is Made

–

– Also called the “Dark Reactions”

• Don’t need light directly, but require the products of the light reactions

– ATP and NADPH generated in the light reactions are used to build molecules of sugar

using carbon dioxide (CO2) in the atmosphere

•

• Starting materials: 3 molecules of carbon dioxide, 12 ATPs, and 6 NADPHs

• The product: one 3-carbon sugar (glyceraldehyde 3-phosphate), which the plant can use to build glucose or other organic molecules

• These products may be used later for cellular respiration in the plant, or for building cell structures

•

• Environmental Impact of Photosynthesis

– Interaction between cellular respiration and photosynthesis

• Food

• Oxygen

•

•

•

• The Greenhouse Effect

– Carbon Dioxide is a greenhouse gas

• Traps heat energy in atmosphere

• Without a Greenhouse Effect, earth would be too cold for life

• Levels of greenhouse gases (like carbon dioxide) have increased since industrial revolution

•

• Considering the process of photosynthesis, how might plants be able to moderate the

greenhouse effect?

•

• All for today…

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1/25/2018

2

Bio 1101 Lec. 5, Part A Chapter 6: Cellular Respiration

•

•

•

–

•

• Energy is needed by cells to do work

– Chemical energy, a form of potential energy, is stored in bonds of food molecules (such as glucose)

– Energy from food is transferred in cellular respiration to high-energy ATP molecules,

which allow the cell to do work

•

•

Cellular Respiration

•

• Multi-step chemical process (metabolic pathway)

• 2 of the 3 steps occur within the mitochondria; the first step occurs outside of the

mitochondria, in the cytoplasm

• Both plant and animal cells use cellular respiration to obtain energy from food molecules

• Reaction occurs in the presence of oxygen

C6H12O6 + 6O2 6CO2 + 6H2O + ATPs (energy)

•

C6H12O6 + 6O2 6CO2 + 6H2O + ATPs (energy)

• In Cellular Respiration, hydrogens are removed from sugar and transferred to oxygen

– Including their electrons

• Redox Reactions (aka Oxidation-Reduction Reactions) involve the transfer of electrons from

one substance to another

– Cellular respiration is therefore a redox reaction

– Electrons (hydrogens) move from glucose to oxygen

–

•

C6H12O6 + 6O2 6CO2 + 6H2O + ATPs (energy)

• In a Redox Reaction:

– The molecule that loses an electron is said to be oxidized

• Glucose is oxidized in cellular respiration

– The molecule that gains electrons is said to be reduced

• Oxygen is reduced in cellular respiration

– Energy is generated because electrons “fall” from a level of higher energy to lower

energy

• The oxygen has a greater affinity for the hydrogen electrons than did the glucose molecule

•

• How do the electrons get to oxygen?

– Via the electron acceptor NAD+

– (Nicotinamide Adenine Dinucleotide)

–Made from niacin (vitamin B3)

–When electrons (hydrogens) are transferred from food to NAD+, it becomes reduced to

NADH

– NADH transports the electrons to the Electron Transport Chain, which ultimately carries

them to the final oxygen acceptor

– This is where most of the energy from food is captured to make ATP

•

• The purpose of cellular respiration: to produce ATP’s – the high-energy molecules that do cellular work

• Cellular respiration is efficient and can produce up to approximately 32 ATP’s

• Step 1: Glycolysis

•

• 1 molecule of Glucose is broken down into 2 molecules of pyruvic acid

– Glucose has 6 carbons

– Pyruvic acid has 3 carbons

• A net of 2 ATP molecules are created from ADPs

– Recall, 2 were used to split glucose

– 2 ATPs were then created from each pyruvic acid

• 2 NADH molecules are created from NAD+ molecules (one per molecule of pyruvic acid)

– NADHs carry electrons to the “electron transport chain,” where most of the ATPs are

created

•

• Step 2: Krebs Cycle (aka Citric Acid Cycle)

– But first, pyruvic acid must be converted to acetyl-CoA

• Pyruvic acid from glycolysis is converted into acetic acid – a 2-carbon compound

• In the process, 2 carbon dioxide molecules are given off

• The acetic acid combines with an enzyme called Co-a, making “Acetyl-CoA”

• Acetyl-CoA is the fuel of the Krebs cycle (aka Citric Acid Cycle)

Krebs Cycle (aka Citric Acid Cycle)

• 2 ATPs are generated directly in the Krebs cycle per glucose

• 6 NADHs and 2 FADH2s are also generated, per glucose

– These molecules carry electrons to the electron transport chain

•

• Krebs Cycle Video:

– https://www.youtube.com/watch?v=uF9XYgLDlFI

• Step 3: Electron Transport Chain (ETC)

– The “machinery” of the ETC is built into the membranes of the mitochondria

• That’s why there are so many inner-foldings of membrane in mitochondria

•

• A series of molecules in the mitochondrial membranes accept electrons

• The first molecule in the chain accepts the electron from NADH

• Passes it on to the next molecule, and so on…

• At each step, energy is given up that is used to make ATPs

– About 28 ATPs produced here!

• Finally, the electrons (and the hydrogen) are accepted by oxygen, making water

•

• Electron Transport Chain Video:

•

• http://www.youtube.com/watch?v=xbJ0nbzt5Kw

• How do organisms obtain energy from food when oxygen isn’t available?

•

• Fermentation…

•

•

•

•

• Ancient organisms likely used glycolysis to make ATP

– No oxygen in the early Earth’s atmosphere

– Today, glycolysis occurs in nearly all organisms

–Must be an ancient metabolic pathway

•

•

• Today, with abundant oxygen, most organisms use cellular respiration

• However, a variety of organisms use anaerobic fermentation

– Fermentation is used by some organisms as their primary metabolic pathway (some

bacteria and yeasts)

–Others switch between fermentation and aerobic respiration, depending on availability of

oxygen

•

• In animals, some cells must function for short periods of time without oxygen

– i.e. when exercising strenuously

• Blood supplies your cells with oxygen for cellular respiration

• If you are consuming energy faster than oxygen, your muscle cells may resort to lactic acid

fermentation to obtain energy

• Very similar to glycolysis (first step of cellular respiration – doesn’t require oxygen)

•

• Fermentation

•

• Much less efficient than cellular respiration, however

–Only 2 ATPs produced, compared to 32 for cellular respiration

– Consume more food molecules to obtain the same amount of energy using fermentation

– Also produces lactic acid as a by-product, which accumulates and makes muscles ache

•

–Microbes that use fermentation as metabolic pathway are used in producing

• Cheeses

• Yogurt

• Bread

• Alcohol

• Soy sauce

• Pickled vegetables

– The CO2 produced by yeasts is also what makes bread rise

•

Bonus Activity

• How is burning a marshmallow similar to/ & different from cellular respiration?

•

• Then, we’ll make s’mores

• For an added biology lesson, let’s look at the ingredients in chocolate

• I used to use Nutella instead of regular chocolate squares, to make “gourmet” s’mores,

BUT:

– Recently learned Nutella and many other chocolate products contain Palm Oil

– Palm Oil is most commonly produced by palm plantations growing in tropical areas; tropical rainforest is cut down to grow these plants; orangutans and tigers are two endangered species that are especially threatened by palm oil plantations

– So, now I look for palm-oil free products

– http://www.youtube.com/watch?v=3I-dxfCaQLU

– http://www.youtube.com/watch?v=oRQWj4H9nH0

• 5-minute break…

•

• Next, Photosynthesis

•

•

•

–

•

Photosynthesis

• Plants are photosynthetic autotrophs

– Generate own food from inorganic ingredients

– Process of photosynthesis is essentially the reverse of cellular respiration:

6CO2 + 6H2O energy C6H12O6 + 6O2

(recall cellular respiration: C6H12O6 + 6O2 6CO2 + 6H2O + energy)

•

• Besides plants, many protists (such as algae, seaweed, microscopic protists like Euglena) and bacteria are also photosynthetic

– In bacteria, photosynthesis doesn’t occur in chloroplasts (recall, prokaryotes do not have membrane-bound organelles)

•

• In eukaryotes, photosynthesis occurs in chloroplasts

•

• Chlorophyll is the pigment in chloroplasts that give them their green color, and absorb light

energy from the sun

•

• In plants, leaves are the structures that contain the most chloroplasts

–Mostly in the mesophyll (“the green tissue in the interior of the leaf”)

•

– Chloroplasts are surrounded by a double membrane

– Inside, filled with thick fluid called stroma

– Suspended in that fluid are stacks of disks called thylakoids; a stack of thylakoids is called a granum

– Photosynthetic pigments (such as chlorophyll) are built into the thylakoid membranes

•

• Photosynthesis consists of two, multi-step processes: the light reactions, and the Calvin

cycle

– Light Reactions – use sunlight to build ATP and NADPH

– Calvin Cycle – uses the energy from the light reactions to build sugar

• Although doesn’t need sunlight directly, can’t synthesize sugar without the ATPs generated in the light reactions

• If runs out of ATPs, can’t build more sugars until sunlight is available to begin the light

reactions again

•

•

• How is the energy from sunlight captured by plants?

•

– Sunlight is a type of electromagnetic energy

– Light travels in waves

• Different colors of light have different wavelengths

• There are also wavelengths of light that are outside of the visible spectrum

•

– Pigments are visible as different colors because they reflect certain wavelengths and absorb others

• Example: the feathers of a cardinal look red because the pigment in them reflects light with a red wavelength, and absorbs the other wavelengths of visible light

– Likewise, leaves of plants appear green because chlorophyll reflects green light

•

• So which wavelengths of light are best used by plants to do photosynthesis?

– Not green, because it is reflected

–Other colors, like reds, oranges, blues, and purples can be absorbed

– Study of bacteria growing in water with algae and seeking oxygen…

•

• There are different types of pigments in plants

– Chlorphyll a – reflects green light, and participates directly in the light reactions

– Chlorophyll b – reflects yellow-green light; may participate indirectly in the light reactions

– Carotenoids – reflect yellow/orange/ light; may pass energy to chlorophyll a, or may protect plant cells by absorbing excess light energy

• Many herbicides work by inhibiting synthesis of carotenoids

• Leads to damage of chlorophyll because free radicals (unpaired electrons) build up and damage molecules

• Plants evolved this strategy to protect their chlorophyll; carotenoids can protect our

cells, too (reducing cancer risk, for example)

•

– Fall colors due to decreases in green chlorophyll, making visible the effects of the carotenoids

•

Step 1 of Photosynthesis: The Light Reactions

• The Light Reactions

• Light Reactions in a nutshell

– Light energy (photons) are absorbed by pigments and used to excite electrons in the water-splitting photosystem

– Excited electrons are accepted by molecules in the electron transport chain (built into the membranes of the thylakoids); oxygen is given off as a by-product

– Energy from the ETC is used to make ATPs (same concept as the ETC in cellular

respiration)

– The electrons then pass to the NADPH-producing photosystem, where they are re-excited by light absorbed by pigment

– The electron is then used to produce NADPH, which is used in the Calvin Cycle

•

• The Calvin Cycle – Where Sugar is Made

–

– Also called the “Dark Reactions”

• Don’t need light directly, but require the products of the light reactions

– ATP and NADPH generated in the light reactions are used to build molecules of sugar

using carbon dioxide (CO2) in the atmosphere

•

• Starting materials: 3 molecules of carbon dioxide, 12 ATPs, and 6 NADPHs

• The product: one 3-carbon sugar (glyceraldehyde 3-phosphate), which the plant can use to build glucose or other organic molecules

• These products may be used later for cellular respiration in the plant, or for building cell structures

•

• Environmental Impact of Photosynthesis

– Interaction between cellular respiration and photosynthesis

• Food

• Oxygen

•

•

•

• The Greenhouse Effect

– Carbon Dioxide is a greenhouse gas

• Traps heat energy in atmosphere

• Without a Greenhouse Effect, earth would be too cold for life

• Levels of greenhouse gases (like carbon dioxide) have increased since industrial revolution

•

• Considering the process of photosynthesis, how might plants be able to moderate the

greenhouse effect?

•

• All for today…

1

2

3

4

5

6

7

8

9

10

11

12

13

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54

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56

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61

1/25/2018

3

Bio 1101 Lec. 5, Part A Chapter 6: Cellular Respiration

•

•

•

–

•

• Energy is needed by cells to do work

– Chemical energy, a form of potential energy, is stored in bonds of food molecules (such as glucose)

– Energy from food is transferred in cellular respiration to high-energy ATP molecules,

which allow the cell to do work

•

•

Cellular Respiration

•

• Multi-step chemical process (metabolic pathway)

• 2 of the 3 steps occur within the mitochondria; the first step occurs outside of the

mitochondria, in the cytoplasm

• Both plant and animal cells use cellular respiration to obtain energy from food molecules

• Reaction occurs in the presence of oxygen

C6H12O6 + 6O2 6CO2 + 6H2O + ATPs (energy)

•

C6H12O6 + 6O2 6CO2 + 6H2O + ATPs (energy)

• In Cellular Respiration, hydrogens are removed from sugar and transferred to oxygen

– Including their electrons

• Redox Reactions (aka Oxidation-Reduction Reactions) involve the transfer of electrons from

one substance to another

– Cellular respiration is therefore a redox reaction

– Electrons (hydrogens) move from glucose to oxygen

–

•

C6H12O6 + 6O2 6CO2 + 6H2O + ATPs (energy)

• In a Redox Reaction:

– The molecule that loses an electron is said to be oxidized

• Glucose is oxidized in cellular respiration

– The molecule that gains electrons is said to be reduced

• Oxygen is reduced in cellular respiration

– Energy is generated because electrons “fall” from a level of higher energy to lower

energy

• The oxygen has a greater affinity for the hydrogen electrons than did the glucose molecule

•

• How do the electrons get to oxygen?

– Via the electron acceptor NAD+

– (Nicotinamide Adenine Dinucleotide)

–Made from niacin (vitamin B3)

–When electrons (hydrogens) are transferred from food to NAD+, it becomes reduced to

NADH

– NADH transports the electrons to the Electron Transport Chain, which ultimately carries

them to the final oxygen acceptor

– This is where most of the energy from food is captured to make ATP

•

• The purpose of cellular respiration: to produce ATP’s – the high-energy molecules that do cellular work

• Cellular respiration is efficient and can produce up to approximately 32 ATP’s

• Step 1: Glycolysis

•

• 1 molecule of Glucose is broken down into 2 molecules of pyruvic acid

– Glucose has 6 carbons

– Pyruvic acid has 3 carbons

• A net of 2 ATP molecules are created from ADPs

– Recall, 2 were used to split glucose

– 2 ATPs were then created from each pyruvic acid

• 2 NADH molecules are created from NAD+ molecules (one per molecule of pyruvic acid)

– NADHs carry electrons to the “electron transport chain,” where most of the ATPs are

created

•

• Step 2: Krebs Cycle (aka Citric Acid Cycle)

– But first, pyruvic acid must be converted to acetyl-CoA

• Pyruvic acid from glycolysis is converted into acetic acid – a 2-carbon compound

• In the process, 2 carbon dioxide molecules are given off

• The acetic acid combines with an enzyme called Co-a, making “Acetyl-CoA”

• Acetyl-CoA is the fuel of the Krebs cycle (aka Citric Acid Cycle)

Krebs Cycle (aka Citric Acid Cycle)

• 2 ATPs are generated directly in the Krebs cycle per glucose

• 6 NADHs and 2 FADH2s are also generated, per glucose

– These molecules carry electrons to the electron transport chain

•

• Krebs Cycle Video:

– https://www.youtube.com/watch?v=uF9XYgLDlFI

• Step 3: Electron Transport Chain (ETC)

– The “machinery” of the ETC is built into the membranes of the mitochondria

• That’s why there are so many inner-foldings of membrane in mitochondria

•

• A series of molecules in the mitochondrial membranes accept electrons

• The first molecule in the chain accepts the electron from NADH

• Passes it on to the next molecule, and so on…

• At each step, energy is given up that is used to make ATPs

– About 28 ATPs produced here!

• Finally, the electrons (and the hydrogen) are accepted by oxygen, making water

•

• Electron Transport Chain Video:

•

• http://www.youtube.com/watch?v=xbJ0nbzt5Kw

• How do organisms obtain energy from food when oxygen isn’t available?

•

• Fermentation…

•

•

•

•

• Ancient organisms likely used glycolysis to make ATP

– No oxygen in the early Earth’s atmosphere

– Today, glycolysis occurs in nearly all organisms

–Must be an ancient metabolic pathway

•

•

• Today, with abundant oxygen, most organisms use cellular respiration

• However, a variety of organisms use anaerobic fermentation

– Fermentation is used by some organisms as their primary metabolic pathway (some

bacteria and yeasts)

–Others switch between fermentation and aerobic respiration, depending on availability of

oxygen

•

• In animals, some cells must function for short periods of time without oxygen

– i.e. when exercising strenuously

• Blood supplies your cells with oxygen for cellular respiration

• If you are consuming energy faster than oxygen, your muscle cells may resort to lactic acid fermentation to obtain energy

• Very similar to glycolysis (first step of cellular respiration – doesn’t require oxygen)

•

• Fermentation

•

• Much less efficient than cellular respiration, however

–Only 2 ATPs produced, compared to 32 for cellular respiration

– Consume more food molecules to obtain the same amount of energy using fermentation

– Also produces lactic acid as a by-product, which accumulates and makes muscles ache

•

–Microbes that use fermentation as metabolic pathway are used in producing

• Cheeses

• Yogurt

• Bread

• Alcohol

• Soy sauce

• Pickled vegetables

– The CO2 produced by yeasts is also what makes bread rise

•

Bonus Activity

• How is burning a marshmallow similar to/ & different from cellular respiration?

•

• Then, we’ll make s’mores

• For an added biology lesson, let’s look at the ingredients in chocolate

• I used to use Nutella instead of regular chocolate squares, to make “gourmet” s’mores,

BUT:

– Recently learned Nutella and many other chocolate products contain Palm Oil

– Palm Oil is most commonly produced by palm plantations growing in tropical areas; tropical rainforest is cut down to grow these plants; orangutans and tigers are two endangered species that are especially threatened by palm oil plantations

– So, now I look for palm-oil free products

– http://www.youtube.com/watch?v=3I-dxfCaQLU

– http://www.youtube.com/watch?v=oRQWj4H9nH0

• 5-minute break…

•

• Next, Photosynthesis

•

•

•

–

•

Photosynthesis

• Plants are photosynthetic autotrophs

– Generate own food from inorganic ingredients

– Process of photosynthesis is essentially the reverse of cellular respiration:

6CO2 + 6H2O energy C6H12O6 + 6O2

(recall cellular respiration: C6H12O6 + 6O2 6CO2 + 6H2O + energy)

•

• Besides plants, many protists (such as algae, seaweed, microscopic protists like Euglena) and bacteria are also photosynthetic

– In bacteria, photosynthesis doesn’t occur in chloroplasts (recall, prokaryotes do not have membrane-bound organelles)

•

• In eukaryotes, photosynthesis occurs in chloroplasts

•

• Chlorophyll is the pigment in chloroplasts that give them their green color, and absorb light

energy from the sun

•

• In plants, leaves are the structures that contain the most chloroplasts

–Mostly in the mesophyll (“the green tissue in the interior of the leaf”)

•

– Chloroplasts are surrounded by a double membrane

– Inside, filled with thick fluid called stroma

– Suspended in that fluid are stacks of disks called thylakoids; a stack of thylakoids is called a granum

– Photosynthetic pigments (such as chlorophyll) are built into the thylakoid membranes

•

• Photosynthesis consists of two, multi-step processes: the light reactions, and the Calvin cycle

– Light Reactions – use sunlight to build ATP and NADPH

– Calvin Cycle – uses the energy from the light reactions to build sugar

• Although doesn’t need sunlight directly, can’t synthesize sugar without the ATPs generated in the light reactions

• If runs out of ATPs, can’t build more sugars until sunlight is available to begin the light

reactions again

•

•

• How is the energy from sunlight captured by plants?

•

– Sunlight is a type of electromagnetic energy

– Light travels in waves

• Different colors of light have different wavelengths

• There are also wavelengths of light that are outside of the visible spectrum

•

– Pigments are visible as different colors because they reflect certain wavelengths and absorb others

• Example: the feathers of a cardinal look red because the pigment in them reflects light with a red wavelength, and absorbs the other wavelengths of visible light

– Likewise, leaves of plants appear green because chlorophyll reflects green light

•

• So which wavelengths of light are best used by plants to do photosynthesis?

– Not green, because it is reflected

–Other colors, like reds, oranges, blues, and purples can be absorbed

– Study of bacteria growing in water with algae and seeking oxygen…

•

• There are different types of pigments in plants

– Chlorphyll a – reflects green light, and participates directly in the light reactions

– Chlorophyll b – reflects yellow-green light; may participate indirectly in the light reactions

– Carotenoids – reflect yellow/orange/ light; may pass energy to chlorophyll a, or may protect plant cells by absorbing excess light energy

• Many herbicides work by inhibiting synthesis of carotenoids

• Leads to damage of chlorophyll because free radicals (unpaired electrons) build up and damage molecules

• Plants evolved this strategy to protect their chlorophyll; carotenoids can protect our

cells, too (reducing cancer risk, for example)

•

– Fall colors due to decreases in green chlorophyll, making visible the effects of the carotenoids

•

Step 1 of Photosynthesis: The Light Reactions

• The Light Reactions

• Light Reactions in a nutshell

– Light energy (photons) are absorbed by pigments and used to excite electrons in the water-splitting photosystem

– Excited electrons are accepted by molecules in the electron transport chain (built into the membranes of the thylakoids); oxygen is given off as a by-product

– Energy from the ETC is used to make ATPs (same concept as the ETC in cellular

respiration)

– The electrons then pass to the NADPH-producing photosystem, where they are re-

excited by light absorbed by pigment

– The electron is then used to produce NADPH, which is used in the Calvin Cycle

•

• The Calvin Cycle – Where Sugar is Made

–

– Also called the “Dark Reactions”

• Don’t need light directly, but require the products of the light reactions

– ATP and NADPH generated in the light reactions are used to build molecules of sugar

using carbon dioxide (CO2) in the atmosphere

•

• Starting materials: 3 molecules of carbon dioxide, 12 ATPs, and 6 NADPHs

• The product: one 3-carbon sugar (glyceraldehyde 3-phosphate), which the plant can use to build glucose or other organic molecules

• These products may be used later for cellular respiration in the plant, or for building cell structures

•

• Environmental Impact of Photosynthesis

– Interaction between cellular respiration and photosynthesis

• Food

• Oxygen

•

•

•

• The Greenhouse Effect

– Carbon Dioxide is a greenhouse gas

• Traps heat energy in atmosphere

• Without a Greenhouse Effect, earth would be too cold for life

• Levels of greenhouse gases (like carbon dioxide) have increased since industrial revolution

•

• Considering the process of photosynthesis, how might plants be able to moderate the

greenhouse effect?

•

• All for today…

1

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1/25/2018

4

Bio 1101 Lec. 5, Part A Chapter 6: Cellular Respiration

•

•

•

–

•

• Energy is needed by cells to do work

– Chemical energy, a form of potential energy, is stored in bonds of food molecules (such as glucose)

– Energy from food is transferred in cellular respiration to high-energy ATP molecules,

which allow the cell to do work

•

•

Cellular Respiration

•

• Multi-step chemical process (metabolic pathway)

• 2 of the 3 steps occur within the mitochondria; the first step occurs outside of the

mitochondria, in the cytoplasm

• Both plant and animal cells use cellular respiration to obtain energy from food molecules

• Reaction occurs in the presence of oxygen

C6H12O6 + 6O2 6CO2 + 6H2O + ATPs (energy)

•

C6H12O6 + 6O2 6CO2 + 6H2O + ATPs (energy)

• In Cellular Respiration, hydrogens are removed from sugar and transferred to oxygen

– Including their electrons

• Redox Reactions (aka Oxidation-Reduction Reactions) involve the transfer of electrons from

one substance to another

– Cellular respiration is therefore a redox reaction

– Electrons (hydrogens) move from glucose to oxygen

–

•

C6H12O6 + 6O2 6CO2 + 6H2O + ATPs (energy)

• In a Redox Reaction:

– The molecule that loses an electron is said to be oxidized

• Glucose is oxidized in cellular respiration

– The molecule that gains electrons is said to be reduced

• Oxygen is reduced in cellular respiration

– Energy is generated because electrons “fall” from a level of higher energy to lower

energy

• The oxygen has a greater affinity for the hydrogen electrons than did the glucose molecule

•

• How do the electrons get to oxygen?

– Via the electron acceptor NAD+

– (Nicotinamide Adenine Dinucleotide)

–Made from niacin (vitamin B3)

–When electrons (hydrogens) are transferred from food to NAD+, it becomes reduced to

NADH

– NADH transports the electrons to the Electron Transport Chain, which ultimately carries

them to the final oxygen acceptor

– This is where most of the energy from food is captured to make ATP

•

• The purpose of cellular respiration: to produce ATP’s – the high-energy molecules that do cellular work

• Cellular respiration is efficient and can produce up to approximately 32 ATP’s

• Step 1: Glycolysis

•

• 1 molecule of Glucose is broken down into 2 molecules of pyruvic acid

– Glucose has 6 carbons

– Pyruvic acid has 3 carbons

• A net of 2 ATP molecules are created from ADPs

– Recall, 2 were used to split glucose

– 2 ATPs were then created from each pyruvic acid

• 2 NADH molecules are created from NAD+ molecules (one per molecule of pyruvic acid)

– NADHs carry electrons to the “electron transport chain,” where most of the ATPs are

created

•

• Step 2: Krebs Cycle (aka Citric Acid Cycle)

– But first, pyruvic acid must be converted to acetyl-CoA

• Pyruvic acid from glycolysis is converted into acetic acid – a 2-carbon compound

• In the process, 2 carbon dioxide molecules are given off

• The acetic acid combines with an enzyme called Co-a, making “Acetyl-CoA”

• Acetyl-CoA is the fuel of the Krebs cycle (aka Citric Acid Cycle)

Krebs Cycle (aka Citric Acid Cycle)

• 2 ATPs are generated directly in the Krebs cycle per glucose

• 6 NADHs and 2 FADH2s are also generated, per glucose

– These molecules carry electrons to the electron transport chain

•

• Krebs Cycle Video:

– https://www.youtube.com/watch?v=uF9XYgLDlFI

• Step 3: Electron Transport Chain (ETC)

– The “machinery” of the ETC is built into the membranes of the mitochondria

• That’s why there are so many inner-foldings of membrane in mitochondria

•

• A series of molecules in the mitochondrial membranes accept electrons

• The first molecule in the chain accepts the electron from NADH

• Passes it on to the next molecule, and so on…

• At each step, energy is given up that is used to make ATPs

– About 28 ATPs produced here!

• Finally, the electrons (and the hydrogen) are accepted by oxygen, making water

•

• Electron Transport Chain Video:

•

• http://www.youtube.com/watch?v=xbJ0nbzt5Kw

• How do organisms obtain energy from food when oxygen isn’t available?

•

• Fermentation…

•

•

•

•

• Ancient organisms likely used glycolysis to make ATP

– No oxygen in the early Earth’s atmosphere

– Today, glycolysis occurs in nearly all organisms

–Must be an ancient metabolic pathway

•

•

• Today, with abundant oxygen, most organisms use cellular respiration

• However, a variety of organisms use anaerobic fermentation

– Fermentation is used by some organisms as their primary metabolic pathway (some

bacteria and yeasts)

–Others switch between fermentation and aerobic respiration, depending on availability of

oxygen

•

• In animals, some cells must function for short periods of time without oxygen

– i.e. when exercising strenuously

• Blood supplies your cells with oxygen for cellular respiration

• If you are consuming energy faster than oxygen, your muscle cells may resort to lactic acid

fermentation to obtain energy

• Very similar to glycolysis (first step of cellular respiration – doesn’t require oxygen)

•

• Fermentation

•

• Much less efficient than cellular respiration, however

–Only 2 ATPs produced, compared to 32 for cellular respiration

– Consume more food molecules to obtain the same amount of energy using fermentation

– Also produces lactic acid as a by-product, which accumulates and makes muscles ache

•

–Microbes that use fermentation as metabolic pathway are used in producing

• Cheeses

• Yogurt

• Bread

• Alcohol

• Soy sauce

• Pickled vegetables

– The CO2 produced by yeasts is also what makes bread rise

•

Bonus Activity

• How is burning a marshmallow similar to/ & different from cellular respiration?

•

• Then, we’ll make s’mores

• For an added biology lesson, let’s look at the ingredients in chocolate

• I used to use Nutella instead of regular chocolate squares, to make “gourmet” s’mores,

BUT:

– Recently learned Nutella and many other chocolate products contain Palm Oil

– Palm Oil is most commonly produced by palm plantations growing in tropical areas; tropical rainforest is cut down to grow these plants; orangutans and tigers are two endangered species that are especially threatened by palm oil plantations

– So, now I look for palm-oil free products

– http://www.youtube.com/watch?v=3I-dxfCaQLU

– http://www.youtube.com/watch?v=oRQWj4H9nH0

• 5-minute break…

•

• Next, Photosynthesis

•

•

•

–

•

Photosynthesis

• Plants are photosynthetic autotrophs

– Generate own food from inorganic ingredients

– Process of photosynthesis is essentially the reverse of cellular respiration:

6CO2 + 6H2O energy C6H12O6 + 6O2

(recall cellular respiration: C6H12O6 + 6O2 6CO2 + 6H2O + energy)

•

• Besides plants, many protists (such as algae, seaweed, microscopic protists like Euglena) and bacteria are also photosynthetic

– In bacteria, photosynthesis doesn’t occur in chloroplasts (recall, prokaryotes do not have membrane-bound organelles)

•

• In eukaryotes, photosynthesis occurs in chloroplasts

•

• Chlorophyll is the pigment in chloroplasts that give them their green color, and absorb light

energy from the sun

•

• In plants, leaves are the structures that contain the most chloroplasts

–Mostly in the mesophyll (“the green tissue in the interior of the leaf”)

•

– Chloroplasts are surrounded by a double membrane

– Inside, filled with thick fluid called stroma

– Suspended in that fluid are stacks of disks called thylakoids; a stack of thylakoids is called a granum

– Photosynthetic pigments (such as chlorophyll) are built into the thylakoid membranes

•

• Photosynthesis consists of two, multi-step processes: the light reactions, and the Calvin

cycle

– Light Reactions – use sunlight to build ATP and NADPH

– Calvin Cycle – uses the energy from the light reactions to build sugar

• Although doesn’t need sunlight directly, can’t synthesize sugar without the ATPs generated in the light reactions

• If runs out of ATPs, can’t build more sugars until sunlight is available to begin the light

reactions again

•

•

• How is the energy from sunlight captured by plants?

•

– Sunlight is a type of electromagnetic energy

– Light travels in waves

• Different colors of light have different wavelengths

• There are also wavelengths of light that are outside of the visible spectrum

•

– Pigments are visible as different colors because they reflect certain wavelengths and absorb others

• Example: the feathers of a cardinal look red because the pigment in them reflects light with a red wavelength, and absorbs the other wavelengths of visible light

– Likewise, leaves of plants appear green because chlorophyll reflects green light

•

• So which wavelengths of light are best used by plants to do photosynthesis?

– Not green, because it is reflected

–Other colors, like reds, oranges, blues, and purples can be absorbed

– Study of bacteria growing in water with algae and seeking oxygen…

•

• There are different types of pigments in plants

– Chlorphyll a – reflects green light, and participates directly in the light reactions

– Chlorophyll b – reflects yellow-green light; may participate indirectly in the light reactions

– Carotenoids – reflect yellow/orange/ light; may pass energy to chlorophyll a, or may protect plant cells by absorbing excess light energy

• Many herbicides work by inhibiting synthesis of carotenoids

• Leads to damage of chlorophyll because free radicals (unpaired electrons) build up and damage molecules

• Plants evolved this strategy to protect their chlorophyll; carotenoids can protect our cells, too (reducing cancer risk, for example)

•

– Fall colors due to decreases in green chlorophyll, making visible the effects of the carotenoids

•

Step 1 of Photosynthesis: The Light Reactions

• The Light Reactions

• Light Reactions in a nutshell

– Light energy (photons) are absorbed by pigments and used to excite electrons in the water-splitting photosystem

– Excited electrons are accepted by molecules in the electron transport chain (built into the membranes of the thylakoids); oxygen is given off as a by-product

– Energy from the ETC is used to make ATPs (same concept as the ETC in cellular

respiration)

– The electrons then pass to the NADPH-producing photosystem, where they are re-

excited by light absorbed by pigment

– The electron is then used to produce NADPH, which is used in the Calvin Cycle

•

• The Calvin Cycle – Where Sugar is Made

–

– Also called the “Dark Reactions”

• Don’t need light directly, but require the products of the light reactions

– ATP and NADPH generated in the light reactions are used to build molecules of sugar

using carbon dioxide (CO2) in the atmosphere

•

• Starting materials: 3 molecules of carbon dioxide, 12 ATPs, and 6 NADPHs

• The product: one 3-carbon sugar (glyceraldehyde 3-phosphate), which the plant can use to build glucose or other organic molecules

• These products may be used later for cellular respiration in the plant, or for building cell structures

•

• Environmental Impact of Photosynthesis

– Interaction between cellular respiration and photosynthesis

• Food

• Oxygen

•

•

•

• The Greenhouse Effect

– Carbon Dioxide is a greenhouse gas

• Traps heat energy in atmosphere

• Without a Greenhouse Effect, earth would be too cold for life

• Levels of greenhouse gases (like carbon dioxide) have increased since industrial revolution

•

• Considering the process of photosynthesis, how might plants be able to moderate the

greenhouse effect?

•

• All for today…

1

2

3

4

5

6

7

8

9

10

11

12

13

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1/25/2018

5

Bio 1101 Lec. 5, Part A Chapter 6: Cellular Respiration

•

•

•

–

•

• Energy is needed by cells to do work

– Chemical energy, a form of potential energy, is stored in bonds of food molecules (such as glucose)

– Energy from food is transferred in cellular respiration to high-energy ATP molecules,

which allow the cell to do work

•

•

Cellular Respiration

•

• Multi-step chemical process (metabolic pathway)

• 2 of the 3 steps occur within the mitochondria; the first step occurs outside of the

mitochondria, in the cytoplasm

• Both plant and animal cells use cellular respiration to obtain energy from food molecules

• Reaction occurs in the presence of oxygen

C6H12O6 + 6O2 6CO2 + 6H2O + ATPs (energy)

•

C6H12O6 + 6O2 6CO2 + 6H2O + ATPs (energy)

• In Cellular Respiration, hydrogens are removed from sugar and transferred to oxygen

– Including their electrons

• Redox Reactions (aka Oxidation-Reduction Reactions) involve the transfer of electrons from

one substance to another

– Cellular respiration is therefore a redox reaction

– Electrons (hydrogens) move from glucose to oxygen

–

•

C6H12O6 + 6O2 6CO2 + 6H2O + ATPs (energy)

• In a Redox Reaction:

– The molecule that loses an electron is said to be oxidized

• Glucose is oxidized in cellular respiration

– The molecule that gains electrons is said to be reduced

• Oxygen is reduced in cellular respiration

– Energy is generated because electrons “fall” from a level of higher energy to lower

energy

• The oxygen has a greater affinity for the hydrogen electrons than did the glucose molecule

•

• How do the electrons get to oxygen?

– Via the electron acceptor NAD+

– (Nicotinamide Adenine Dinucleotide)

–Made from niacin (vitamin B3)

–When electrons (hydrogens) are transferred from food to NAD+, it becomes reduced to

NADH

– NADH transports the electrons to the Electron Transport Chain, which ultimately carries

them to the final oxygen acceptor

– This is where most of the energy from food is captured to make ATP

•

• The purpose of cellular respiration: to produce ATP’s – the high-energy molecules that do cellular work

• Cellular respiration is efficient and can produce up to approximately 32 ATP’s

• Step 1: Glycolysis

•

• 1 molecule of Glucose is broken down into 2 molecules of pyruvic acid

– Glucose has 6 carbons

– Pyruvic acid has 3 carbons

• A net of 2 ATP molecules are created from ADPs

– Recall, 2 were used to split glucose

– 2 ATPs were then created from each pyruvic acid

• 2 NADH molecules are created from NAD+ molecules (one per molecule of pyruvic acid)

– NADHs carry electrons to the “electron transport chain,” where most of the ATPs are

created

•

• Step 2: Krebs Cycle (aka Citric Acid Cycle)

– But first, pyruvic acid must be converted to acetyl-CoA

• Pyruvic acid from glycolysis is converted into acetic acid – a 2-carbon compound

• In the process, 2 carbon dioxide molecules are given off

• The acetic acid combines with an enzyme called Co-a, making “Acetyl-CoA”

• Acetyl-CoA is the fuel of the Krebs cycle (aka Citric Acid Cycle)

Krebs Cycle (aka Citric Acid Cycle)

• 2 ATPs are generated directly in the Krebs cycle per glucose

• 6 NADHs and 2 FADH2s are also generated, per glucose

– These molecules carry electrons to the electron transport chain

•

• Krebs Cycle Video:

– https://www.youtube.com/watch?v=uF9XYgLDlFI

• Step 3: Electron Transport Chain (ETC)

– The “machinery” of the ETC is built into the membranes of the mitochondria

• That’s why there are so many inner-foldings of membrane in mitochondria

•

• A series of molecules in the mitochondrial membranes accept electrons

• The first molecule in the chain accepts the electron from NADH

• Passes it on to the next molecule, and so on…

• At each step, energy is given up that is used to make ATPs

– About 28 ATPs produced here!

• Finally, the electrons (and the hydrogen) are accepted by oxygen, making water

•

• Electron Transport Chain Video:

•

• http://www.youtube.com/watch?v=xbJ0nbzt5Kw

• How do organisms obtain energy from food when oxygen isn’t available?

•

• Fermentation…

•

•

•

•

• Ancient organisms likely used glycolysis to make ATP

– No oxygen in the early Earth’s atmosphere

– Today, glycolysis occurs in nearly all organisms

–Must be an ancient metabolic pathway

•

•

• Today, with abundant oxygen, most organisms use cellular respiration

• However, a variety of organisms use anaerobic fermentation

– Fermentation is used by some organisms as their primary metabolic pathway (some

bacteria and yeasts)

–Others switch between fermentation and aerobic respiration, depending on availability of

oxygen

•

• In animals, some cells must function for short periods of time without oxygen

– i.e. when exercising strenuously

• Blood supplies your cells with oxygen for cellular respiration

• If you are consuming energy faster than oxygen, your muscle cells may resort to lactic acid

fermentation to obtain energy

• Very similar to glycolysis (first step of cellular respiration – doesn’t require oxygen)

•

• Fermentation

•

• Much less efficient than cellular respiration, however

–Only 2 ATPs produced, compared to 32 for cellular respiration

– Consume more food molecules to obtain the same amount of energy using fermentation

– Also produces lactic acid as a by-product, which accumulates and makes muscles ache

•

–Microbes that use fermentation as metabolic pathway are used in producing

• Cheeses

• Yogurt

• Bread

• Alcohol

• Soy sauce

• Pickled vegetables

– The CO2 produced by yeasts is also what makes bread rise

•

Bonus Activity

• How is burning a marshmallow similar to/ & different from cellular respiration?

•

• Then, we’ll make s’mores

• For an added biology lesson, let’s look at the ingredients in chocolate

• I used to use Nutella instead of regular chocolate squares, to make “gourmet” s’mores,

BUT:

– Recently learned Nutella and many other chocolate products contain Palm Oil

– Palm Oil is most commonly produced by palm plantations growing in tropical areas; tropical rainforest is cut down to grow these plants; orangutans and tigers are two endangered species that are especially threatened by palm oil plantations

– So, now I look for palm-oil free products

– http://www.youtube.com/watch?v=3I-dxfCaQLU

– http://www.youtube.com/watch?v=oRQWj4H9nH0

• 5-minute break…

•

• Next, Photosynthesis

•

•

•

–

•

Photosynthesis

• Plants are photosynthetic autotrophs

– Generate own food from inorganic ingredients

– Process of photosynthesis is essentially the reverse of cellular respiration:

6CO2 + 6H2O energy C6H12O6 + 6O2

(recall cellular respiration: C6H12O6 + 6O2 6CO2 + 6H2O + energy)

•

• Besides plants, many protists (such as algae, seaweed, microscopic protists like Euglena) and bacteria are also photosynthetic

– In bacteria, photosynthesis doesn’t occur in chloroplasts (recall, prokaryotes do not have membrane-bound organelles)

•

• In eukaryotes, photosynthesis occurs in chloroplasts

•

• Chlorophyll is the pigment in chloroplasts that give them their green color, and absorb light

energy from the sun

•

• In plants, leaves are the structures that contain the most chloroplasts

–Mostly in the mesophyll (“the green tissue in the interior of the leaf”)

•

– Chloroplasts are surrounded by a double membrane

– Inside, filled with thick fluid called stroma

– Suspended in that fluid are stacks of disks called thylakoids; a stack of thylakoids is called a granum

– Photosynthetic pigments (such as chlorophyll) are built into the thylakoid membranes

•

• Photosynthesis consists of two, multi-step processes: the light reactions, and the Calvin

cycle

– Light Reactions – use sunlight to build ATP and NADPH

– Calvin Cycle – uses the energy from the light reactions to build sugar

• Although doesn’t need sunlight directly, can’t synthesize sugar without the ATPs generated in the light reactions

• If runs out of ATPs, can’t build more sugars until sunlight is available to begin the light

reactions again

•

•

• How is the energy from sunlight captured by plants?

•

– Sunlight is a type of electromagnetic energy

– Light travels in waves

• Different colors of light have different wavelengths

• There are also wavelengths of light that are outside of the visible spectrum

•

– Pigments are visible as different colors because they reflect certain wavelengths and absorb others

• Example: the feathers of a cardinal look red because the pigment in them reflects light with a red wavelength, and absorbs the other wavelengths of visible light

– Likewise, leaves of plants appear green because chlorophyll reflects green light

•

• So which wavelengths of light are best used by plants to do photosynthesis?

– Not green, because it is reflected

–Other colors, like reds, oranges, blues, and purples can be absorbed

– Study of bacteria growing in water with algae and seeking oxygen…

•

• There are different types of pigments in plants

– Chlorphyll a – reflects green light, and participates directly in the light reactions

– Chlorophyll b – reflects yellow-green light; may participate indirectly in the light reactions

– Carotenoids – reflect yellow/orange/ light; may pass energy to chlorophyll a, or may protect plant cells by absorbing excess light energy

• Many herbicides work by inhibiting synthesis of carotenoids

• Leads to damage of chlorophyll because free radicals (unpaired electrons) build up and damage molecules

• Plants evolved this strategy to protect their chlorophyll; carotenoids can protect our

cells, too (reducing cancer risk, for example)

•

– Fall colors due to decreases in green chlorophyll, making visible the effects of the carotenoids

•

Step 1 of Photosynthesis: The Light Reactions

• The Light Reactions

• Light Reactions in a nutshell

– Light energy (photons) are absorbed by pigments and used to excite electrons in the water-splitting photosystem

– Excited electrons are accepted by molecules in the electron transport chain (built into the membranes of the thylakoids); oxygen is given off as a by-product

– Energy from the ETC is used to make ATPs (same concept as the ETC in cellular

respiration)

– The electrons then pass to the NADPH-producing photosystem, where they are re-

excited by light absorbed by pigment

– The electron is then used to produce NADPH, which is used in the Calvin Cycle

•

• The Calvin Cycle – Where Sugar is Made

–

– Also called the “Dark Reactions”

• Don’t need light directly, but require the products of the light reactions

– ATP and NADPH generated in the light reactions are used to build molecules of sugar

using carbon dioxide (CO2) in the atmosphere

•

• Starting materials: 3 molecules of carbon dioxide, 12 ATPs, and 6 NADPHs

• The product: one 3-carbon sugar (glyceraldehyde 3-phosphate), which the plant can use to build glucose or other organic molecules

• These products may be used later for cellular respiration in the plant, or for building cell structures

•

• Environmental Impact of Photosynthesis

– Interaction between cellular respiration and photosynthesis

• Food

• Oxygen

•

•

•

• The Greenhouse Effect

– Carbon Dioxide is a greenhouse gas

• Traps heat energy in atmosphere

• Without a Greenhouse Effect, earth would be too cold for life

• Levels of greenhouse gases (like carbon dioxide) have increased since industrial revolution

•

• Considering the process of photosynthesis, how might plants be able to moderate the

greenhouse effect?

•

• All for today…

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

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23

24

25

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41

42

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48

49

50

51

52

53

54

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61

1/25/2018

6

Bio 1101 Lec. 5, Part A Chapter 6: Cellular Respiration

•

•

•

–

•

• Energy is needed by cells to do work

– Chemical energy, a form of potential energy, is stored in bonds of food molecules (such as glucose)

– Energy from food is transferred in cellular respiration to high-energy ATP molecules,

which allow the cell to do work

•

•

Cellular Respiration

•

• Multi-step chemical process (metabolic pathway)

• 2 of the 3 steps occur within the mitochondria; the first step occurs outside of the mitochondria, in the cytoplasm

• Both plant and animal cells use cellular respiration to obtain energy from food molecules

• Reaction occurs in the presence of oxygen

C6H12O6 + 6O2 6CO2 + 6H2O + ATPs (energy)

•

C6H12O6 + 6O2 6CO2 + 6H2O + ATPs (energy)

• In Cellular Respiration, hydrogens are removed from sugar and transferred to oxygen

– Including their electrons

• Redox Reactions (aka Oxidation-Reduction Reactions) involve the transfer of electrons from

one substance to another

– Cellular respiration is therefore a redox reaction

– Electrons (hydrogens) move from glucose to oxygen

–

•

C6H12O6 + 6O2 6CO2 + 6H2O + ATPs (energy)

• In a Redox Reaction:

– The molecule that loses an electron is said to be oxidized

• Glucose is oxidized in cellular respiration

– The molecule that gains electrons is said to be reduced

• Oxygen is reduced in cellular respiration

– Energy is generated because electrons “fall” from a level of higher energy to lower energy

• The oxygen has a greater affinity for the hydrogen electrons than did the glucose molecule

•

• How do the electrons get to oxygen?

– Via the electron acceptor NAD+

– (Nicotinamide Adenine Dinucleotide)

–Made from niacin (vitamin B3)

–When electrons (hydrogens) are transferred from food to NAD+, it becomes reduced to

NADH

– NADH transports the electrons to the Electron Transport Chain, which ultimately carries

them to the final oxygen acceptor

– This is where most of the energy from food is captured to make ATP

•

• The purpose of cellular respiration: to produce ATP’s – the high-energy molecules that do cellular work

• Cellular respiration is efficient and can produce up to approximately 32 ATP’s

• Step 1: Glycolysis

•

• 1 molecule of Glucose is broken down into 2 molecules of pyruvic acid

– Glucose has 6 carbons

– Pyruvic acid has 3 carbons

• A net of 2 ATP molecules are created from ADPs

– Recall, 2 were used to split glucose

– 2 ATPs were then created from each pyruvic acid

• 2 NADH molecules are created from NAD+ molecules (one per molecule of pyruvic acid)

– NADHs carry electrons to the “electron transport chain,” where most of the ATPs are created

•

• Step 2: Krebs Cycle (aka Citric Acid Cycle)

– But first, pyruvic acid must be converted to acetyl-CoA

• Pyruvic acid from glycolysis is converted into acetic acid – a 2-carbon compound

• In the process, 2 carbon dioxide molecules are given off

• The acetic acid combines with an enzyme called Co-a, making “Acetyl-CoA”

• Acetyl-CoA is the fuel of the Krebs cycle (aka Citric Acid Cycle)

Krebs Cycle (aka Citric Acid Cycle)

• 2 ATPs are generated directly in the Krebs cycle per glucose

• 6 NADHs and 2 FADH2s are also generated, per glucose

– These molecules carry electrons to the electron transport chain

•

• Krebs Cycle Video:

– https://www.youtube.com/watch?v=uF9XYgLDlFI

• Step 3: Electron Transport Chain (ETC)

– The “machinery” of the ETC is built into the membranes of the mitochondria

• That’s why there are so many inner-foldings of membrane in mitochondria

•

• A series of molecules in the mitochondrial membranes accept electrons

• The first molecule in the chain accepts the electron from NADH

• Passes it on to the next molecule, and so on…

• At each step, energy is given up that is used to make ATPs

– About 28 ATPs produced here!

• Finally, the electrons (and the hydrogen) are accepted by oxygen, making water

•

• Electron Transport Chain Video:

•

• http://www.youtube.com/watch?v=xbJ0nbzt5Kw

• How do organisms obtain energy from food when oxygen isn’t available?

•

• Fermentation…

•

•

•

•

• Ancient organisms likely used glycolysis to make ATP

– No oxygen in the early Earth’s atmosphere

– Today, glycolysis occurs in nearly all organisms

–Must be an ancient metabolic pathway

•

•

• Today, with abundant oxygen, most organisms use cellular respiration

• However, a variety of organisms use anaerobic fermentation

– Fermentation is used by some organisms as their primary metabolic pathway (some

bacteria and yeasts)

–Others switch between fermentation and aerobic respiration, depending on availability of

oxygen

•

• In animals, some cells must function for short periods of time without oxygen

– i.e. when exercising strenuously

• Blood supplies your cells with oxygen for cellular respiration

• If you are consuming energy faster than oxygen, your muscle cells may resort to lactic acid

fermentation to obtain energy

• Very similar to glycolysis (first step of cellular respiration – doesn’t require oxygen)

•

• Fermentation

•

• Much less efficient than cellular respiration, however

–Only 2 ATPs produced, compared to 32 for cellular respiration

– Consume more food molecules to obtain the same amount of energy using fermentation

– Also produces lactic acid as a by-product, which accumulates and makes muscles ache

•

–Microbes that use fermentation as metabolic pathway are used in producing

• Cheeses

• Yogurt

• Bread

• Alcohol

• Soy sauce

• Pickled vegetables

– The CO2 produced by yeasts is also what makes bread rise

•

Bonus Activity

• How is burning a marshmallow similar to/ & different from cellular respiration?

•

• Then, we’ll make s’mores

• For an added biology lesson, let’s look at the ingredients in chocolate

• I used to use Nutella instead of regular chocolate squares, to make “gourmet” s’mores,

BUT:

– Recently learned Nutella and many other chocolate products contain Palm Oil

– Palm Oil is most commonly produced by palm plantations growing in tropical areas; tropical rainforest is cut down to grow these plants; orangutans and tigers are two endangered species that are especially threatened by palm oil plantations

– So, now I look for palm-oil free products

– http://www.youtube.com/watch?v=3I-dxfCaQLU

– http://www.youtube.com/watch?v=oRQWj4H9nH0

• 5-minute break…

•

• Next, Photosynthesis

•

•

•

–

•

Photosynthesis

• Plants are photosynthetic autotrophs

– Generate own food from inorganic ingredients

– Process of photosynthesis is essentially the reverse of cellular respiration:

6CO2 + 6H2O energy C6H12O6 + 6O2

(recall cellular respiration: C6H12O6 + 6O2 6CO2 + 6H2O + energy)

•

• Besides plants, many protists (such as algae, seaweed, microscopic protists like Euglena) and bacteria are also photosynthetic

– In bacteria, photosynthesis doesn’t occur in chloroplasts (recall, prokaryotes do not have membrane-bound organelles)

•

• In eukaryotes, photosynthesis occurs in chloroplasts

•

• Chlorophyll is the pigment in chloroplasts that give them their green color, and absorb light

energy from the sun

•

• In plants, leaves are the structures that contain the most chloroplasts

–Mostly in the mesophyll (“the green tissue in the interior of the leaf”)

•

– Chloroplasts are surrounded by a double membrane

– Inside, filled with thick fluid called stroma

– Suspended in that fluid are stacks of disks called thylakoids; a stack of thylakoids is called a granum

– Photosynthetic pigments (such as chlorophyll) are built into the thylakoid membranes

•

• Photosynthesis consists of two, multi-step processes: the light reactions, and the Calvin

cycle

– Light Reactions – use sunlight to build ATP and NADPH

– Calvin Cycle – uses the energy from the light reactions to build sugar

• Although doesn’t need sunlight directly, can’t synthesize sugar without the ATPs generated in the light reactions

• If runs out of ATPs, can’t build more sugars until sunlight is available to begin the light reactions again

•

•

• How is the energy from sunlight captured by plants?

•

– Sunlight is a type of electromagnetic energy

– Light travels in waves

• Different colors of light have different wavelengths

• There are also wavelengths of light that are outside of the visible spectrum

•

– Pigments are visible as different colors because they reflect certain wavelengths and absorb others

• Example: the feathers of a cardinal look red because the pigment in them reflects light with a red wavelength, and absorbs the other wavelengths of visible light

– Likewise, leaves of plants appear green because chlorophyll reflects green light

•

• So which wavelengths of light are best used by plants to do photosynthesis?

– Not green, because it is reflected

–Other colors, like reds, oranges, blues, and purples can be absorbed

– Study of bacteria growing in water with algae and seeking oxygen…

•

• There are different types of pigments in plants

– Chlorphyll a – reflects green light, and participates directly in the light reactions

– Chlorophyll b – reflects yellow-green light; may participate indirectly in the light reactions

– Carotenoids – reflect yellow/orange/ light; may pass energy to chlorophyll a, or may protect plant cells by absorbing excess light energy

• Many herbicides work by inhibiting synthesis of carotenoids

• Leads to damage of chlorophyll because free radicals (unpaired electrons) build up and damage molecules

• Plants evolved this strategy to protect their chlorophyll; carotenoids can protect our

cells, too (reducing cancer risk, for example)

•

– Fall colors due to decreases in green chlorophyll, making visible the effects of the carotenoids

•

Step 1 of Photosynthesis: The Light Reactions

• The Light Reactions

• Light Reactions in a nutshell

– Light energy (photons) are absorbed by pigments and used to excite electrons in the water-splitting photosystem

– Excited electrons are accepted by molecules in the electron transport chain (built into the membranes of the thylakoids); oxygen is given off as a by-product

– Energy from the ETC is used to make ATPs (same concept as the ETC in cellular

respiration)

– The electrons then pass to the NADPH-producing photosystem, where they are re-

excited by light absorbed by pigment

– The electron is then used to produce NADPH, which is used in the Calvin Cycle

•

• The Calvin Cycle – Where Sugar is Made

–

– Also called the “Dark Reactions”

• Don’t need light directly, but require the products of the light reactions

– ATP and NADPH generated in the light reactions are used to build molecules of sugar

using carbon dioxide (CO2) in the atmosphere

•

• Starting materials: 3 molecules of carbon dioxide, 12 ATPs, and 6 NADPHs

• The product: one 3-carbon sugar (glyceraldehyde 3-phosphate), which the plant can use to build glucose or other organic molecules

• These products may be used later for cellular respiration in the plant, or for building cell structures

•

• Environmental Impact of Photosynthesis

– Interaction between cellular respiration and photosynthesis

• Food

• Oxygen

•

•

•

• The Greenhouse Effect

– Carbon Dioxide is a greenhouse gas

• Traps heat energy in atmosphere

• Without a Greenhouse Effect, earth would be too cold for life

• Levels of greenhouse gases (like carbon dioxide) have increased since industrial revolution

•

• Considering the process of photosynthesis, how might plants be able to moderate the

greenhouse effect?

•

• All for today…

1

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3

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1/25/2018

7

Bio 1101 Lec. 5, Part A Chapter 6: Cellular Respiration

•

•

•

–

•

• Energy is needed by cells to do work

– Chemical energy, a form of potential energy, is stored in bonds of food molecules (such as glucose)

– Energy from food is transferred in cellular respiration to high-energy ATP molecules, which allow the cell to do work

•

•

Cellular Respiration

•

• Multi-step chemical process (metabolic pathway)

• 2 of the 3 steps occur within the mitochondria; the first step occurs outside of the

mitochondria, in the cytoplasm

• Both plant and animal cells use cellular respiration to obtain energy from food molecules

• Reaction occurs in the presence of oxygen

C6H12O6 + 6O2 6CO2 + 6H2O + ATPs (energy)

•

C6H12O6 + 6O2 6CO2 + 6H2O + ATPs (energy)

• In Cellular Respiration, hydrogens are removed from sugar and transferred to oxygen

– Including their electrons

• Redox Reactions (aka Oxidation-Reduction Reactions) involve the transfer of electrons from

one substance to another

– Cellular respiration is therefore a redox reaction

– Electrons (hydrogens) move from glucose to oxygen

–

•

C6H12O6 + 6O2 6CO2 + 6H2O + ATPs (energy)

• In a Redox Reaction:

– The molecule that loses an electron is said to be oxidized

• Glucose is oxidized in cellular respiration

– The molecule that gains electrons is said to be reduced

• Oxygen is reduced in cellular respiration

– Energy is generated because electrons “fall” from a level of higher energy to lower

energy

• The oxygen has a greater affinity for the hydrogen electrons than did the glucose molecule

•

• How do the electrons get to oxygen?

– Via the electron acceptor NAD+

– (Nicotinamide Adenine Dinucleotide)

–Made from niacin (vitamin B3)

–When electrons (hydrogens) are transferred from food to NAD+, it becomes reduced to

NADH

– NADH transports the electrons to the Electron Transport Chain, which ultimately carries

them to the final oxygen acceptor

– This is where most of the energy from food is captured to make ATP

•

• The purpose of cellular respiration: to produce ATP’s – the high-energy molecules that do cellular work

• Cellular respiration is efficient and can produce up to approximately 32 ATP’s

• Step 1: Glycolysis

•

• 1 molecule of Glucose is broken down into 2 molecules of pyruvic acid

– Glucose has 6 carbons

– Pyruvic acid has 3 carbons

• A net of 2 ATP molecules are created from ADPs

– Recall, 2 were used to split glucose

– 2 ATPs were then created from each pyruvic acid

• 2 NADH molecules are created from NAD+ molecules (one per molecule of pyruvic acid)

– NADHs carry electrons to the “electron transport chain,” where most of the ATPs are

created

•

• Step 2: Krebs Cycle (aka Citric Acid Cycle)

– But first, pyruvic acid must be converted to acetyl-CoA

• Pyruvic acid from glycolysis is converted into acetic acid – a 2-carbon compound

• In the process, 2 carbon dioxide molecules are given off

• The acetic acid combines with an enzyme called Co-a, making “Acetyl-CoA”

• Acetyl-CoA is the fuel of the Krebs cycle (aka Citric Acid Cycle)

Krebs Cycle (aka Citric Acid Cycle)

• 2 ATPs are generated directly in the Krebs cycle per glucose

• 6 NADHs and 2 FADH2s are also generated, per glucose

– These molecules carry electrons to the electron transport chain

•

• Krebs Cycle Video:

– https://www.youtube.com/watch?v=uF9XYgLDlFI

• Step 3: Electron Transport Chain (ETC)

– The “machinery” of the ETC is built into the membranes of the mitochondria

• That’s why there are so many inner-foldings of membrane in mitochondria

•

• A series of molecules in the mitochondrial membranes accept electrons

• The first molecule in the chain accepts the electron from NADH

• Passes it on to the next molecule, and so on…

• At each step, energy is given up that is used to make ATPs

– About 28 ATPs produced here!

• Finally, the electrons (and the hydrogen) are accepted by oxygen, making water

•

• Electron Transport Chain Video:

•

• http://www.youtube.com/watch?v=xbJ0nbzt5Kw

• How do organisms obtain energy from food when oxygen isn’t available?

•

• Fermentation…

•

•

•

•

• Ancient organisms likely used glycolysis to make ATP

– No oxygen in the early Earth’s atmosphere

– Today, glycolysis occurs in nearly all organisms

–Must be an ancient metabolic pathway

•

•

• Today, with abundant oxygen, most organisms use cellular respiration

• However, a variety of organisms use anaerobic fermentation

– Fermentation is used by some organisms as their primary metabolic pathway (some

bacteria and yeasts)

–Others switch between fermentation and aerobic respiration, depending on availability of

oxygen

•

• In animals, some cells must function for short periods of time without oxygen

– i.e. when exercising strenuously

• Blood supplies your cells with oxygen for cellular respiration

• If you are consuming energy faster than oxygen, your muscle cells may resort to lactic acid

fermentation to obtain energy

• Very similar to glycolysis (first step of cellular respiration – doesn’t require oxygen)

•

• Fermentation

•

• Much less efficient than cellular respiration, however

–Only 2 ATPs produced, compared to 32 for cellular respiration

– Consume more food molecules to obtain the same amount of energy using fermentation

– Also produces lactic acid as a by-product, which accumulates and makes muscles ache

•

–Microbes that use fermentation as metabolic pathway are used in producing

• Cheeses

• Yogurt

• Bread

• Alcohol

• Soy sauce

• Pickled vegetables

– The CO2 produced by yeasts is also what makes bread rise

•

Bonus Activity

• How is burning a marshmallow similar to/ & different from cellular respiration?

•

• Then, we’ll make s’mores

• For an added biology lesson, let’s look at the ingredients in chocolate

• I used to use Nutella instead of regular chocolate squares, to make “gourmet” s’mores,

BUT:

– Recently learned Nutella and many other chocolate products contain Palm Oil

– Palm Oil is most commonly produced by palm plantations growing in tropical areas; tropical rainforest is cut down to grow these plants; orangutans and tigers are two endangered species that are especially threatened by palm oil plantations

– So, now I look for palm-oil free products

– http://www.youtube.com/watch?v=3I-dxfCaQLU

– http://www.youtube.com/watch?v=oRQWj4H9nH0

• 5-minute break…

•

• Next, Photosynthesis

•

•

•

–

•

Photosynthesis

• Plants are photosynthetic autotrophs

– Generate own food from inorganic ingredients

– Process of photosynthesis is essentially the reverse of cellular respiration:

6CO2 + 6H2O energy C6H12O6 + 6O2

(recall cellular respiration: C6H12O6 + 6O2 6CO2 + 6H2O + energy)

•

• Besides plants, many protists (such as algae, seaweed, microscopic protists like Euglena) and bacteria are also photosynthetic

– In bacteria, photosynthesis doesn’t occur in chloroplasts (recall, prokaryotes do not have membrane-bound organelles)

•

• In eukaryotes, photosynthesis occurs in chloroplasts

•

• Chlorophyll is the pigment in chloroplasts that give them their green color, and absorb light

energy from the sun

•

• In plants, leaves are the structures that contain the most chloroplasts

–Mostly in the mesophyll (“the green tissue in the interior of the leaf”)

•

– Chloroplasts are surrounded by a double membrane

– Inside, filled with thick fluid called stroma

– Suspended in that fluid are stacks of disks called thylakoids; a stack of thylakoids is called a granum

– Photosynthetic pigments (such as chlorophyll) are built into the thylakoid membranes

•

• Photosynthesis consists of two, multi-step processes: the light reactions, and the Calvin

cycle

– Light Reactions – use sunlight to build ATP and NADPH

– Calvin Cycle – uses the energy from the light reactions to build sugar

• Although doesn’t need sunlight directly, can’t synthesize sugar without the ATPs generated in the light reactions

• If runs out of ATPs, can’t build more sugars until sunlight is available to begin the light

reactions again

•

•

• How is the energy from sunlight captured by plants?

•

– Sunlight is a type of electromagnetic energy

– Light travels in waves

• Different colors of light have different wavelengths

• There are also wavelengths of light that are outside of the visible spectrum

•

– Pigments are visible as different colors because they reflect certain wavelengths and absorb others

• Example: the feathers of a cardinal look red because the pigment in them reflects light with a red wavelength, and absorbs the other wavelengths of visible light

– Likewise, leaves of plants appear green because chlorophyll reflects green light

•

• So which wavelengths of light are best used by plants to do photosynthesis?

– Not green, because it is reflected

–Other colors, like reds, oranges, blues, and purples can be absorbed

– Study of bacteria growing in water with algae and seeking oxygen…

•

• There are different types of pigments in plants

– Chlorphyll a – reflects green light, and participates directly in the light reactions

– Chlorophyll b – reflects yellow-green light; may participate indirectly in the light reactions

– Carotenoids – reflect yellow/orange/ light; may pass energy to chlorophyll a, or may protect plant cells by absorbing excess light energy

• Many herbicides work by inhibiting synthesis of carotenoids

• Leads to damage of chlorophyll because free radicals (unpaired electrons) build up and damage molecules

• Plants evolved this strategy to protect their chlorophyll; carotenoids can protect our

cells, too (reducing cancer risk, for example)

•

– Fall colors due to decreases in green chlorophyll, making visible the effects of the carotenoids

•

Step 1 of Photosynthesis: The Light Reactions

• The Light Reactions

• Light Reactions in a nutshell

– Light energy (photons) are absorbed by pigments and used to excite electrons in the water-splitting photosystem

– Excited electrons are accepted by molecules in the electron transport chain (built into the membranes of the thylakoids); oxygen is given off as a by-product

– Energy from the ETC is used to make ATPs (same concept as the ETC in cellular

respiration)

– The electrons then pass to the NADPH-producing photosystem, where they are re-

excited by light absorbed by pigment

– The electron is then used to produce NADPH, which is used in the Calvin Cycle

•

• The Calvin Cycle – Where Sugar is Made

–

– Also called the “Dark Reactions”

• Don’t need light directly, but require the products of the light reactions

– ATP and NADPH generated in the light reactions are used to build molecules of sugar

using carbon dioxide (CO2) in the atmosphere

•

• Starting materials: 3 molecules of carbon dioxide, 12 ATPs, and 6 NADPHs

• The product: one 3-carbon sugar (glyceraldehyde 3-phosphate), which the plant can use to build glucose or other organic molecules

• These products may be used later for cellular respiration in the plant, or for building cell structures

•

• Environmental Impact of Photosynthesis

– Interaction between cellular respiration and photosynthesis

• Food

• Oxygen

•

•

•

• The Greenhouse Effect

– Carbon Dioxide is a greenhouse gas

• Traps heat energy in atmosphere

• Without a Greenhouse Effect, earth would be too cold for life

• Levels of greenhouse gases (like carbon dioxide) have increased since industrial revolution

•

• Considering the process of photosynthesis, how might plants be able to moderate the

greenhouse effect?

•

• All for today…

1

2

3

4

5

6

7

8

9

10

11

12

13

14

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16

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1/25/2018

8

Bio 1101 Lec. 5, Part A Chapter 6: Cellular Respiration

•

•

•

–

•

• Energy is needed by cells to do work

– Chemical energy, a form of potential energy, is stored in bonds of food molecules (such as glucose)

– Energy from food is transferred in cellular respiration to high-energy ATP molecules,

which allow the cell to do work

•

•

Cellular Respiration

•

• Multi-step chemical process (metabolic pathway)

• 2 of the 3 steps occur within the mitochondria; the first step occurs outside of the

mitochondria, in the cytoplasm

• Both plant and animal cells use cellular respiration to obtain energy from food molecules

• Reaction occurs in the presence of oxygen

C6H12O6 + 6O2 6CO2 + 6H2O + ATPs (energy)

•

C6H12O6 + 6O2 6CO2 + 6H2O + ATPs (energy)

• In Cellular Respiration, hydrogens are removed from sugar and transferred to oxygen

– Including their electrons

• Redox Reactions (aka Oxidation-Reduction Reactions) involve the transfer of electrons from

one substance to another

– Cellular respiration is therefore a redox reaction

– Electrons (hydrogens) move from glucose to oxygen

–

•

C6H12O6 + 6O2 6CO2 + 6H2O + ATPs (energy)

• In a Redox Reaction:

– The molecule that loses an electron is said to be oxidized

• Glucose is oxidized in cellular respiration

– The molecule that gains electrons is said to be reduced

• Oxygen is reduced in cellular respiration

– Energy is generated because electrons “fall” from a level of higher energy to lower

energy

• The oxygen has a greater affinity for the hydrogen electrons than did the glucose molecule

•

• How do the electrons get to oxygen?

– Via the electron acceptor NAD+

– (Nicotinamide Adenine Dinucleotide)

–Made from niacin (vitamin B3)

–When electrons (hydrogens) are transferred from food to NAD+, it becomes reduced to

NADH

– NADH transports the electrons to the Electron Transport Chain, which ultimately carries

them to the final oxygen acceptor

– This is where most of the energy from food is captured to make ATP

•

• The purpose of cellular respiration: to produce ATP’s – the high-energy molecules that do cellular work

• Cellular respiration is efficient and can produce up to approximately 32 ATP’s

• Step 1: Glycolysis

•

• 1 molecule of Glucose is broken down into 2 molecules of pyruvic acid

– Glucose has 6 carbons

– Pyruvic acid has 3 carbons

• A net of 2 ATP molecules are created from ADPs

– Recall, 2 were used to split glucose

– 2 ATPs were then created from each pyruvic acid

• 2 NADH molecules are created from NAD+ molecules (one per molecule of pyruvic acid)

– NADHs carry electrons to the “electron transport chain,” where most of the ATPs are

created

•

• Step 2: Krebs Cycle (aka Citric Acid Cycle)

– But first, pyruvic acid must be converted to acetyl-CoA

• Pyruvic acid from glycolysis is converted into acetic acid – a 2-carbon compound

• In the process, 2 carbon dioxide molecules are given off

• The acetic acid combines with an enzyme called Co-a, making “Acetyl-CoA”

• Acetyl-CoA is the fuel of the Krebs cycle (aka Citric Acid Cycle)

Krebs Cycle (aka Citric Acid Cycle)

• 2 ATPs are generated directly in the Krebs cycle per glucose

• 6 NADHs and 2 FADH2s are also generated, per glucose

– These molecules carry electrons to the electron transport chain

•

• Krebs Cycle Video:

– https://www.youtube.com/watch?v=uF9XYgLDlFI

• Step 3: Electron Transport Chain (ETC)

– The “machinery” of the ETC is built into the membranes of the mitochondria

• That’s why there are so many inner-foldings of membrane in mitochondria

•

• A series of molecules in the mitochondrial membranes accept electrons

• The first molecule in the chain accepts the electron from NADH

• Passes it on to the next molecule, and so on…

• At each step, energy is given up that is used to make ATPs

– About 28 ATPs produced here!

• Finally, the electrons (and the hydrogen) are accepted by oxygen, making water

•

• Electron Transport Chain Video:

•

• http://www.youtube.com/watch?v=xbJ0nbzt5Kw

• How do organisms obtain energy from food when oxygen isn’t available?

•

• Fermentation…

•

•

•

•

• Ancient organisms likely used glycolysis to make ATP

– No oxygen in the early Earth’s atmosphere

– Today, glycolysis occurs in nearly all organisms

–Must be an ancient metabolic pathway

•

•

• Today, with abundant oxygen, most organisms use cellular respiration

• However, a variety of organisms use anaerobic fermentation

– Fermentation is used by some organisms as their primary metabolic pathway (some

bacteria and yeasts)

–Others switch between fermentation and aerobic respiration, depending on availability of

oxygen

•

• In animals, some cells must function for short periods of time without oxygen

– i.e. when exercising strenuously

• Blood supplies your cells with oxygen for cellular respiration

• If you are consuming energy faster than oxygen, your muscle cells may resort to lactic acid

fermentation to obtain energy

• Very similar to glycolysis (first step of cellular respiration – doesn’t require oxygen)

•

• Fermentation

•

• Much less efficient than cellular respiration, however

–Only 2 ATPs produced, compared to 32 for cellular respiration

– Consume more food molecules to obtain the same amount of energy using fermentation

– Also produces lactic acid as a by-product, which accumulates and makes muscles ache

•

–Microbes that use fermentation as metabolic pathway are used in producing

• Cheeses

• Yogurt

• Bread

• Alcohol

• Soy sauce

• Pickled vegetables

– The CO2 produced by yeasts is also what makes bread rise

•

Bonus Activity

• How is burning a marshmallow similar to/ & different from cellular respiration?

•

• Then, we’ll make s’mores

• For an added biology lesson, let’s look at the ingredients in chocolate

• I used to use Nutella instead of regular chocolate squares, to make “gourmet” s’mores,

BUT:

– Recently learned Nutella and many other chocolate products contain Palm Oil

– Palm Oil is most commonly produced by palm plantations growing in tropical areas; tropical rainforest is cut down to grow these plants; orangutans and tigers are two endangered species that are especially threatened by palm oil plantations

– So, now I look for palm-oil free products

– http://www.youtube.com/watch?v=3I-dxfCaQLU

– http://www.youtube.com/watch?v=oRQWj4H9nH0

• 5-minute break…

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• Next, Photosynthesis

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Photosynthesis

• Plants are photosynthetic autotrophs

– Generate own food from inorganic ingredients

– Process of photosynthesis is essentially the reverse of cellular respiration:

6CO2 + 6H2O energy C6H12O6 + 6O2

(recall cellular respiration: C6H12O6 + 6O2 6CO2 + 6H2O + energy)

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• Besides plants, many protists (such as algae, seaweed, microscopic protists like Euglena) and bacteria are also photosynthetic

– In bacteria, photosynthesis doesn’t occur in chloroplasts (recall, prokaryotes do not have membrane-bound organelles)

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• In eukaryotes, photosynthesis occurs in chloroplasts

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• Chlorophyll is the pigment in chloroplasts that give them their green color, and absorb light

energy from the sun

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• In plants, leaves are the structures that contain the most chloroplasts

–Mostly in the mesophyll (“the green tissue in the interior of the leaf”)

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– Chloroplasts are surrounded by a double membrane

– Inside, filled with thick fluid called stroma

– Suspended in that fluid are stacks of disks called thylakoids; a stack of thylakoids is called a granum

– Photosynthetic pigments (such as chlorophyll) are built into the thylakoid membranes

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• Photosynthesis consists of two, multi-step processes: the light reactions, and the Calvin

cycle

– Light Reactions – use sunlight to build ATP and NADPH

– Calvin Cycle – uses the energy from the light reactions to build sugar

• Although doesn’t need sunlight directly, can’t synthesize sugar without the ATPs generated in the light reactions

• If runs out of ATPs, can’t build more sugars until sunlight is available to begin the light

reactions again

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• How is the energy from sunlight captured by plants?

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– Sunlight is a type of electromagnetic energy

– Light travels in waves

• Different colors of light have different wavelengths

• There are also wavelengths of light that are outside of the visible spectrum

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– Pigments are visible as different colors because they reflect certain wavelengths and absorb others

• Example: the feathers of a cardinal look red because the pigment in them reflects light with a red wavelength, and absorbs the other wavelengths of visible light

– Likewise, leaves of plants appear green because chlorophyll reflects green light

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• So which wavelengths of light are best used by plants to do photosynthesis?

– Not green, because it is reflected

–Other colors, like reds, oranges, blues, and purples can be absorbed

– Study of bacteria growing in water with algae and seeking oxygen…

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• There are different types of pigments in plants

– Chlorphyll a – reflects green light, and participates directly in the light reactions

– Chlorophyll b – reflects yellow-green light; may participate indirectly in the light reactions

– Carotenoids – reflect yellow/orange/ light; may pass energy to chlorophyll a, or may protect plant cells by absorbing excess light energy

• Many herbicides work by inhibiting synthesis of carotenoids

• Leads to damage of chlorophyll because free radicals (unpaired electrons) build up and damage molecules

• Plants evolved this strategy to protect their chlorophyll; carotenoids can protect our

cells, too (reducing cancer risk, for example)

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– Fall colors due to decreases in green chlorophyll, making visible the effects of the carotenoids

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Step 1 of Photosynthesis: The Light Reactions

• The Light Reactions

• Light Reactions in a nutshell

– Light energy (photons) are absorbed by pigments and used to excite electrons in the water-splitting photosystem

– Excited electrons are accepted by molecules in the electron transport chain (built into the membranes of the thylakoids); oxygen is given off as a by-product

– Energy from the ETC is used to make ATPs (same concept as the ETC in cellular

respiration)

– The electrons then pass to the NADPH-producing photosystem, where they are re-excited by light absorbed by pigment

– The electron is then used to produce NADPH, which is used in the Calvin Cycle

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• The Calvin Cycle – Where Sugar is Made

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– Also called the “Dark Reactions”

• Don’t need light directly, but require the products of the light reactions

– ATP and NADPH generated in the light reactions are used to build molecules of sugar

using carbon dioxide (CO2) in the atmosphere

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• Starting materials: 3 molecules of carbon dioxide, 12 ATPs, and 6 NADPHs

• The product: one 3-carbon sugar (glyceraldehyde 3-phosphate), which the plant can use to build glucose or other organic molecules

• These products may be used later for cellular respiration in the plant, or for building cell structures

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• Environmental Impact of Photosynthesis

– Interaction between cellular respiration and photosynthesis

• Food

• Oxygen

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• The Greenhouse Effect

– Carbon Dioxide is a greenhouse gas

• Traps heat energy in atmosphere

• Without a Greenhouse Effect, earth would be too cold for life

• Levels of greenhouse gases (like carbon dioxide) have increased since industrial revolution

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• Considering the process of photosynthesis, how might plants be able to moderate the

greenhouse effect?

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• All for today…

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