respiration &...

Respiration &Photosynthesis

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Usually, energy flows into ecosystems as light from the sun and leaves as heat.

Photosynthesis uses the energy in sunlight to generate oxygen and glucose; while trapping carbon.

Cellular respiration uses that glucose to generate ATP, which supplies useable energy for cells while releasing carbon and absorbing oxygen. Cells use ATP to generate.

The overall effect is for solar energy to be transformed to energy that is used by life; and then finally heat. Much of that heat is then radiated away from Earth as infrared radiation.

Energy and Life

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Energy and Life

decomposers(bacteria, fungi)

Abiotic Chemicals

(CO2, O2, N,minerals)

Producers(plants)

consumers(herbivores,carnivores)HEAT

HEAT

HEAT

HEAT

HEAT

C

O

O

O O

NFe Solar

Energy

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The Production of ATPCatabolic Pathways

Recall that catabolism is that aspect of metabolism involved in breaking down molecules to release energy.

Cellular respiration is a catabolic pathway that consumes oxygen and organic molecules and yields ATP.

Carbohydrates, fats, and proteins can all fuel cellular respiration.

We'll look first at the simplest case, the breakdown of the sugar - glucose.

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C6H12O6 + 6O2 ⇒ 6CO2 + 6H2O + ATP

The breakdown of organic molecules is exergonic, it releases energy.

Catabolic pathways yield energy by oxidizing organic fuels.

This is the balanced chemical reaction, when O2 is available, for the combustion of glucose to provide energy to cells:

The Production of ATPCatabolic Pathways

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The shuttle boosters use the rapid combustion of fuel to power 4.4 billion pounds away from Earth.

While the chemical process of cellular respiration is similar to this powerful reaction, cells must use a much more carefully-controlled process to get useable energy from the combustion of glucose.

Combustion Reactions

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Cellular Respiration

There are two types of cellular respiration:

· Anaerobic - which occurs without the use of oxygen

· Aerobic - which requires the use of oxygen

Both forms share the same first step: Glycolysis

So let's talk about that first, then we can discuss the two types of respiration that follow from that first stage

But before doing that we have to learn about two molecules that are essential to respiration

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NAD+ + 2H+ + 2e- + Energy NADH + H+

NAD+ and FAD

The molecules NAD+ and FAD are used to store, and later release, energy during respiration; they are key to respiration.

Each molecules has two forms, each form stores a different amount of energy. So moving between those two forms either stores chemical potential energy or releases it.

Here are the reactions:

FAD + 2H+ + 2e- + Energy FADH2

The double arrows indicate that each reaction is reversible, they can proceed in either direction. When the reaction goes to the right, energy is stored. When it goes to the left, energy is released

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NAD+ and FAD

The amount of energy that is useable when the reaction goes to the left, depends on the availability of O2 . Without the presence of O2, the energy stored in NADH and FADH2 cannot be used to make ATP.

If O2 is present,

· 1 NADH stores enough energy to create about 3 ATPs

· 1 FADH2 stores enough energy to make about 2 ATPs



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1 Anaerobic processes _____.

A require the use of oxygen

B do not require the use of oxygen

C require the use of hydrogen

D do not require the use of hydrogen

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2 Aerobic processes _____.

A require the use of oxygen

B do not require the use of oxygen

C require the use of hydrogen

D do not require the use of hydrogen

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3 NADH is converted to NAD+. During this process, _____.

A energy is released

B energy is stored

C no energy is stored or released

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4 NAD+ is converted to NADH. During this process, _____.


B energy is stored

C no energy is released or stored

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5 FAD is converted to FADH2. During this process, _____.


B energy is stored


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6 FADH2 is converted to FAD. During this process, _____.


B energy is stored


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Reduction and Oxidation

When we go from left to right we are adding electrons to a molecule. That is called reducing the molecule, or the process of reduction.

Going from right to left, we are taking electrons from a molecule. That is called oxidizing the molecule, or the process of oxidation.



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The reason for the term oxidation is that this is the effect that oxygen usually has: it takes electrons from a molecule, oxidizing the molecule

The rusting of iron is an example of oxidation: oxygen is taking electrons from the metal, oxidizing it.

Oxidation

4 Fe + 3 O2 → 2 Fe2O3

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Reduction and Oxydation

LEO says GER

Losing Electrons is Oxidation

Gaining Electrons is Reduction

Since it doesn't seem right that adding electrons is called "reduction"; here's a way to remember these two terms.

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7 When a molecule is oxidized, electrons are removed from it.

True

False

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8 When a molecule is reduced, electrons are removed from it.

True

False

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C6H12O6(Glucose)

Gycolysis

2 ATP

4 ATP2 NADH

2 C3H4O3 (Pyruvate)

2 NAD+

Glycolysis

This is the first stage of both anaerobic and aerobic respiration.It involves the breakdown of glucose, a 6 carbon sugar, into 2 molecules of pyruvate, a 3 carbon sugar.

Glycolysis means the splitting of glucose

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C6H12O6(Glucose)

Gycolysis

2 ATP

4 ATP2 NADH

2 C3H4O3 (Pyruvate)

2 NAD+

Glycolysis


Some ATP is needed to start the process, but the net result is :

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C6H12O6(Glucose)

Gycolysis

2 ATP

4 ATP2 NADH

2 C3H4O3 (Pyruvate)

2 NAD+

Glycolysis


Some ATP is needed to start the process, but the net result is :

a net of 2 ATPs are formed along with 2 NADHs and the 2 pryuvates.

note: 2 ATP go into the reaction, 4 come out of the reaction - which gives the NET of 2

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Fermentation

Without O2, the energy stored in NADH2 and pyruvate can't be used.

The net energy gain of anaerobic respiration is just 2 ATPs. (Remember 2 were invested and 4 were produced, netting 2)

However, the Pyruvate still needs to be cleared from the cell, and the NADH converted back to NAD+ to begin another cycle.

The process of doing this is called fermentation.

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9 The process of glylcolyis requires oxygen.

True

False

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Fermentation

2 NADH

2 NAD+

2 C3H4O3 (Pyruvate)

CO2 & 2 Ethanol

2 LacticAcid

Lactic AcidFermentation

EthanolFermentation

OR

FermentationFermentation breaks down the products of glycolysis so that glycolysis can be repeated with another glucose molecule.

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Fermentation

2 NADH

2 NAD+

2 C3H4O3 (Pyruvate)

CO2 & 2 Ethanol

2 LacticAcid


EthanolFermentation

OR


1 glucose molecule had yielded 2 ATPs, 2 Pyruvates and 2 NADHs. That is the input to the fermentation stage of anaerobic respiration.

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Fermentation

2 NADH

2 NAD+

2 C3H4O3 (Pyruvate)

CO2 & 2 Ethanol

2 LacticAcid


EthanolFermentation

OR



The pyruvates and NADHs are fermented into 2 NAD+ and either Lactic Acid or

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Fermentation

2 NADH

2 NAD+

2 C3H4O3 (Pyruvate)

CO2 & 2 Ethanol

2 LacticAcid


EthanolFermentation

OR



The pyruvates and NADHs are fermented into 2 NAD+ and either Lactic Acid or CO2 & Ethanol.

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Anaerobic Respiration

The result of the combined steps of glycolysis and fermentation is:

· The input is 1 Glucose + 2 ATP molecules

· The output is 4 ATP molecules (for a net gain of 2 ATP's)

In addition,

· Lactic Acid fermentation results in lactic acid

· Ethanol fermentation results in ethanol and CO2

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For about the first 2.0 BY of life on Earth, before oxygen became prevalent in the atmosphere about 2.5 BYA, there was only anaerobic respiration.

But even now, it is the only means of cellular respiration in oxygen-poor environments.

Anaerobic Respiration

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· Anaerobic organisms live in oxygen-poor environments and rely on glycolysis and fermentation for energy.

· The alcohol in wine, beer, etc. results from yeast undergoing ethanol fermentation.

· Bread rises due to the release of CO2 bubbles by fermenting yeast.

· Your muscles burn after a strenuous workout because they can't get enough O2, so they perform Lactic Acid Fermentation. Lactic acid results in soreness.

Examples of Anaerobic Respiration

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Breweries force yeast to do alcohol fermentation by supplying them with food called mash (hops, barley) while at the same time depriving the yeast of oxygen by filling airtight containers with water.

Alcohol Fermentation

The final product is beer

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2005 was the closest finish in the history of the NYC Marathon

They had run 26.2 miles, stride for stride and were tied.

Both men began to sprint to the finish.

Lactic Acid Fermentation

Paul Tergat vs. Hendrick Ramaala

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Paul Teragat won by less than 1 second!


What made the difference?

How did he manage to beat his opponent?

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When runners run for long distances they "keep pace", which means their cells never use more oxygen than can be replenished in muscle cells.

When sprinting, oxygen runs out and lactic acid fermentation takes over in an attempt to make ATP without oxygen.


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Lactic acid build up causes muscles to burn.


Both runners were equally matched for cellular respirationbut Tergat's muscles were able to withstand the pain of lactic acid fermentation better than Henrick's.

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10 The two types of fermentation are called

A Alcoholic and Aerobic.

B Aerobic and Anaerobic.

C Ethanol and Lactic Acid.

D Lactic acid and Anaerobic.

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11 Alcoholic fermentation occurs in

A humans

B yeastC aerobic bateriaD none of the above

E all of the above

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12 The starting molecule for glycolysis is _____.

A ADP

B pyruvic acid

C citric acid

D glucose

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13 Glycolysis requires _____.

A an energy input

B oxygen

C hours to produce many ATP molecules

D NADP+

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14 How many ATP molecules are needed as input for glycolysis to proceed on 2 glucose molecules?

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15 How many ATP molecules are needed as input for glycolysis to proceed on 7 Glucose molecules?

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16 How many net ATP molecules are generated by the glycolysis of 9 glucose molecules?

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17 How many pyruvate molecules are generated by the glycolysis of 4 glucose molecules?

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18 What element was missing from the atmosphere of early Earth, when glycolysis and fermentation was the only stage of cellular respiration?

A Hydrogen

B Oxygen

C Mercury

D Nitrogen

E None of the Above

F All of the above

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19 What is a possible product of glycolysis and/or fermentation?

A Alcohol

B CO2

C Pyruvate

D Lactic Acid

E None of the Above

F All of the above

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For the first 2.0 BY of life on Earth, anaerobic respiration was the only means of obtaining energy from food.

But then, the Oxygen Revolution occurred about 2.5 BYA, flooding the planet with oxygen.

This led to made much more energy available to life, enabling the much more complex food chains we see today.

Oxygen Revolution

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Some bacteria, called facultative bacteria, after the glycolysis stage, can either go on to fermentation or, if O2 is available, aerobic respiration.

Your muscles do that as well: that's the difference between aerobic workouts and anaerobic workouts .

Similarities between Bacteria and Muscles

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The big difference is that for each glucose molecule

aerobic respiration yields 36 to 38 ATPs

anaerobic respiration yields only 2 ATPs

Aerobic vs. Anaerobic Respiration

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The Stages of Aerobic Respiration

Aerobic respiration consists of four stages:

· Glycolysis · The Pyruvate Dehydrogenase Complex (PDC)· The Citric Acid Cycle· Oxidative Phosphorylation

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The first stage, glycolysis, is the exactly the same as it is in the first stage of anaerobic respiration.

Glycolysis first breaks down glucose into two molecules of pyruvate (pyruvic acid)

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Pyruvate Dehydrogenase Complex (PDC) converts the 3-carbon pyruvate into a 2-carbon molecule that can be used in the Citric Acid Cycle.

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The Citric Acid Cycle completes the breakdown of glucose, starting with the products of the PDC

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The Electron Transport Chain (ETC) and Oxidative Phosphorylation (OP) uses the energy stored in NADH and FADH2 to perform most of the ATP synthesis

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C6H12O6(Glucose)

Gycolysis

2 ATP

4 ATP2 NADH

2 NAD+

2 C3H4O3 (Pyruvate)

GlycolysisThis stage is identical to that used in anaerobic respiration..

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C6H12O6(Glucose)

Gycolysis

2 ATP

4 ATP2 NADH

2 NAD+

2 C3H4O3 (Pyruvate)


It involves the breakdown of glucose, a 6 carbon sugar, into 2 molecules of pyruvate, a 3 carbon sugar.

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C6H12O6(Glucose)

Gycolysis

2 ATP

4 ATP2 NADH

2 NAD+

2 C3H4O3 (Pyruvate)


It involves the breakdown of glucose, a 6 carbon sugar, into 2 molecules of pyruvate, a 3 carbon sugar.

Some ATP is needed to start the process, but the net result is: 2 ATPs are formed along with 2 NADHs and 2 pryuvates.

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The Pyruvate Dehydrogenase Complex (PDC)

The Citric Acid Cycle can only process 2-carbon molecules, and pyruvate is a 3-carbon molecule: C3H4O3

PDC

2 NADH

2 NAD+

2 C3H4O3 (Pyruvate)

2 CO2

2 Acetyl Co-A

2 O2 The PDC takes the 2 pyruvate molecules and converts them to 2 Acetyl Co-A molecules: these are 2 carbon molecules.

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The Pyruvate Dehydrogenase Complex (PDC)

The Citric Acid Cycle can only process 2-carbon molecules, and pyruvate is a 3-carbon molecule: C3H4O3

PDC

2 NADH

2 NAD+

2 C3H4O3 (Pyruvate)

2 CO2

2 Acetyl Co-A

2 O2 The PDC takes the 2 pyruvate molecules and converts them to 2 Acetyl Co-A molecules: these are 2 carbon molecules.

In doing this energy is stored by the conversion of 2 NAD+ to 2 NADH and 2 O2 molecules carry away the extra pyruvate carbons as CO2.

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20 During the PDC ______.

A Pyruvate is converted to Acetyl Co-A

B NAD+ is converterd to NADH

C CO2 is emitted

D All of the above

E None of the above

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21 The PDC is a ______ process.

A anaerboic

B fermentation

C aerobic

D All of the above

E None of the above

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The citric acid cycle is sometimes called the Krebs cycle.

The cycle breaks down one Acetyl Co-A for each turn, generating 1 ATP, 3 NADH, 2 CO2 and 1 FADH2 per Acetyl Co-A.

This supplies the NADH and FADH2 that are required to drive the Electron Transport Process (ETP): the next stage of respiration.

Since 2 Acetyl Co-A molecules were created from each glucose, the Citric Acid Cylce creates 2 ATP; 6 NADH; 4CO2, and 2 FADH2 for each glucose molecule.

The Citric Acid Cycle

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This shows one cycle, which is due to one Acetyl Co-A molecule.

To account for one glucose molecule, two cycles are needed.

Let's tally up the output for one cycle to confirm our results.

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The Citric Acid CycleThis is one turn of the cycle, due to 1 Acetyl Co-A. Note the production of:

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1 ATP

This is one turn of the cycle, due to 1 Acetyl Co-A. Note the production of:

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1 ATP3 NADH


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1 ATP3 NADH1 FADH2


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1 ATP3 NADH1 FADH2

2 ATP6 NADH2 FADH2

But 1 glucose molecule, yields 2 Acetyl Co-A molecules, (therefore, 2 turns of the cycle) yielding :


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22 The Citric Acid Cycle does not require oxygen.

True

False

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23 How many of the following would be produced with three turns of the citric acid cycle?

A 1 ATP, 2 CO2, 3 NADH, and 1 FADH2

B 2 ATP, 2 CO2, 1 NADH, and 3 FADH2

C 3 ATP, 3 CO2, 3 NADH, and 3 FADH2

D 3 ATP, 6 CO2, 9 NADH, and 3 FADH2

E 38 ATP, 6 CO2, 3 NADH, and 12 FADH2

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24 The key molecule that is fed into the Citric Acid Cycle is _______.

A Glucose

B Pyruvate

C Carbon Dioxide

D Oxygen

E Acetyl Co-A

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25 How many carbon atoms are fed into the citric acid cycle from one molecule of pyruvate?

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26 The products of the Citric Acid Cycle are ___ molecules of NADH, ___ molecules of ATP and ___ molecules of FADH2.

A 1, 3, 1

B 2, 3, 1

C 2, 3, 3

D 3, 1, 1

E 1 , 1, 1

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So far we've done a lot of work to just get a net gain of 4 ATPs.

But we have stored a lot of potential energy in the form of NADH and FADH2.

The big energy payoff is in this stage, where we convert the energy stored in those molecules to ATP.

Electron Transport Chain (ETC) and Oxidative Phosphorylation (OP)

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Stage NADH FADH2 ATP

Glycolysis 2 0 2

PDC 2 0 0

CAC 6 2 2

Total 10 2 4


We're now going to convert all the NADH and FADH2 into ATP, so the energy can be stored throughout the cell.

Here's what we start this cycle with.

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Stage NADH FADH2 ATP

Glycolysis 2 0 2

PDC 2 0 0

CAC 6 2 2

Total 10 2 4


We get about 3 ATPs per NADH and 2 ATPs per FADH2. So how many ATPs should we have at the end of this next stage?

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Here's how that conversion to ATP takes place.

The Electron Transport Chain (ETC) creates a proton gradient to be to drive Oxidative Phosphorylation. This has the same effect as charging a battery.

The process of Oxidative Phosphorylation uses the potential energy of the gradient created by ETC to create a current of protons that drives the enzyme ATP Synthase, adding the third phosphate group to ADP, making ATP.

ETC and OP

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The ETC generates no ATP, but enables Oxidative Phosphorylation, which accounts for most of the ATP produced.

The ETC’s function is to break the large free-energy drop from food into smaller steps that release energy in manageable amounts.

The final electron acceptor of the electron transport chain is O2; forming water (H2O).

O2 strongly attracts electrons in order to fill its outer shell. That attraction pulls electrons through the ETC.

The Electron Transport Chain (ETC)

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One way to think of the ETC is as a proton pump.

This process transports electrons, through chemical reactions, out and then back through a plasma membrane. The net effect is to pump protons from the inside to the outside of a plasma membrane.


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This gives the inside of the membrane a negative charge, due to a shortage of protons, and the outside of the membrane a positive charge, due to an excess of protons. This can be thought of as a proton gradient.

This electric potential represents stored energy, just like a battery; it can do work.


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Electrons are pulled through a path that weaves back and forth through the plasma membrane. They pull protons along with them; protons are attracted to electrons.

On each trip out of the plasma membrane, the protons that travel with them are left outside, but the electrons move back inside. In their final reaction, they combine with O2 to form H2O.


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This creates an electric potential that can be used to make ATP via chemiosmosis.

This process can only take place near a plasma membrane. We'll see that bacteria use their cell's membrane for this purpose, while eukaryotes use the membranes of their mitochondria.


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

http://www.youtube .com/watch?v=3y1dO4nNaKY&feature=re lated

The electron path is shown in black.


The proton path in red.

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The ETC creates a positive electrostatic potential outside the plasma membrane and a negative potential inside. The excess protons outside, are strongly attracted to the inside, but are blocked by the membrane. One path is open to the protons, but they must do work to use it.

ATP Synthase is essentially a motor, constructed of proteins. The protons must travel through that motor in order to return to the cell, creating an electric current that powers the motor.

As the motor turns, it adds a phosphate group to ADP, creating ATP. Electrical energy is transformed to chemical energy.

This is an example of chemiosmosis, the use of energy in a H+ gradient to drive cellular work

Oxidative PhosphorylationChemiosmosis

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http://njc.tl/tl

http://njc.tl/tm


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27 Which metabolic pathway is common to both aerobic and anaerobic cellular respiration?

A the citric acid cycle

B the electron transport chain

C glycolysis

D synthesis of acetyl CoA from pyruvate

E reduction of pyruvate to lactate

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28 ATP Synthase relies on the facilitated diffusion of ______ down their gradient to produce ATP.

A electrons

B protons

C glucose

D oxygen

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29 The final reaction of the electrons in the ETC is to bond with _____ to create ______.

A glucose, ATP

B protons, ATP

C hydrogen, glucose

D oxygen, water

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30 Anaerboic respiration produces ___ ATPs while aerobic respiration produces between ____ and ____ ATPs.

A 4, 26, 38

B 2, 48, 58

C 2, 26, 38

D 2, 36, 38

E 4, 38, 54

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We calculated earlier that we would expect to get 38 ATP molecules by the time we'd converted all the NADH and FADH2 to ATP.

The actual yield is between 36 - 38 ATP molecules per glucose molecule.

The reason for the small variance is that in some cases energy is needed to transport the NADH molecules to the site of the ETC.

(But 36 to 38 ATPs per glucose is a lot better than 2, the yield from the anaerobic process.)

Aerobic Respiration

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Oxidative PhosphorylationThe Hydroelectric Analogy

The Hoover Dam is a massive structure that holds back the potential energy of 9 trillion gallons of water

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Like oxidative phosphorylation,it creates a gradient then exploits the stored energy by allowing water to pass through a small pipeline, transforming it to kinetic energy.


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Massive turbines are spun, causing the kinetic energy to be turned into mechanical energy which is utilized to make electrical energy.


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31 Which of the following is the correct sequence of events in aerobic respiration?

A glycolysis, PDC, ETC, citric acid cycle

B citric acid cycle, ETC, PDC, glycolysis

C glycolysis, PDC, citric acid cycle, ETC

D citric acid cycle, glycolysis, ETC, PDC

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32 Which process could be compared to how rushing water turns an electric generator?

A the citric acid cycle

B glycolysis

C formation of NADH in glycolysis

D oxidative phosphorylation

E the electron transport system

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33 In chemiosmosis, what is the most direct source of energy that is used to convert ADP to ATP?

A energy released as electrons flow through the electron transport system

B energy released from substrate-level phosphorylation

C energy released from ATP synthase pumping hydrogen ions against their concentration gradient

D energy released from movement of protons through ATP synthase

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34 Energy released by the electron transport chain is used to pump H+ ions into which location?

A outside the membrane

B inside the membrane

C into the membrane

D oxygen

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35 About how many ATP molecules are produced from the complete oxidation of 2 glucose molecules?

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36 The final electron acceptor of the electron transport chain that functions in oxidative phosphorylation is ______.

A oxygen

B water

C NAD+

D pyruvate

E ADP

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The Versatility of Catabolism

Catabolic pathways funnel electrons from many kinds of organic molecules into cellular respiration.

· Glycolysis accepts a wide range of carbohydrates

· Proteins must be digested to amino acids; amino groups can feed glycolysis or the citric acid cycle

· Fats are digested to glycerol which is used in glycolysis. An oxidized gram of fat produces more than twice as much ATP as an oxidized gram of carbohydrate

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The Versatility of Catabolism

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37 What is the term for metabolic pathways that release stored energy by breaking down complex molecules?

A anabolic pathways

B catabolic pathways

C fermentation pathways

D thermodynamic pathways

E bioenergetic pathways

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38 Glycolysis is thought to be one of the most ancient of metabolic processes. Which statement supports this idea?

A Glycolysis is used by all cells.

B Glycolysis neither uses nor needs O2.

C Ancient prokaryotic cells made extensive use of glycolysis long before oxygen was present in Earth's atmosphere.

D None of the above

E All of the above

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39 An organism consumes large amounts of sugar, yet does not gain much weight when denied air. Its consumption of sugar increases as air is removed from its environment. When returned to normal air, the organism does fine. Which of the following best describes the organism?

A It must use a molecule other than oxygen to accept electrons from the electron transport chain.

B It is a normal eukaryotic organism.

C The organismobviously lacks the citric acid cycle and electron transport chain.

D It is an anaerobic organism.

E It is a facultative organism: capable of doing anaerobic and aerobic cellular respiration.

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Respiration gets energy from glucose and stores it as ATP.

But what is the source of glucose?

And, where did the oxygen that flooded Earth 2.5 BYA come from?

Photosynthesis

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Here's the balanced chemical equation for aerobic respiration:

And here's the balanced chemical equation for photosynthesis:

C6H12O6 + 6O2 6CO2 + 6H2O + ATP

6CO2 + 6H2O + Light Energy C6H12O6 + 6O2

Aerobic Respiration V. Photosynthesis

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Aerobic respiration uses oxygen (O2) and glucose (C6H12O6) to create carbon dioxide (CO2) and water (H2O)...and release energy.

C6H12O6 + 6O2 6CO2 + 6H2O + ATP

6CO2 + 6H2O + Light Energy C6H12O6 + 6O2 Photosynthesis is the exact opposite, it takes carbon dioxide (CO2) and water (H2O) plus energy to make glucose (C6H12O6) and oxygen (O2)

Aerobic Respiration V. Photosynthesis

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Photosynthesis and Respiration

Summing these two equations reveals that the ATP used by cells is derived from light energy, from the sun. That is the source of energy for most life on Earth.

C6H12O6 + 6O2 6CO2 + 6H2O + ATP (Energy)


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Light Energy ATP (Energy)

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Except for a small number of bacteria that live on chemical reactions in challenging environments, the energy for all life on Earth comes from these processes...from the energy of sunlight. Even though not every organism undergoes photosythesis, the products that plants produce are used in reactions that consumers use. In this way, you can say that . . .

You are solar powered!

Light Energy ATP (Energy)


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40 What are the reactants of cellular respiration?

A oxygen and water

B glucose and carbon dioxide

C glucose and water

D glucose and oxygen

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41 What are the products of photosynthesis?

A glucose and oxygen

B oxygen and water

C glucose and carbon dioxide

D carbon dioxide and water

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42 What are the reactants of photosynthesis?

A carbon dioxide and water

B oxygen and water

C glucose and oxygen

D glucose and carbon dioxide

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43 Photosynthesis ____________ energy, whereas cellular respiration __________ energy.

A consumes, produces

B produces, consumes

C produces, produces

D consumes, consumes

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44 The source of energy for photosynthesis is ______.

A electric energy

B light

C heat

D kinetic energy

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What is the source of glucose?

Where did the oxygen that flooded Earth 2.5 BYA come from?

Our Original Questions

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The products of photosynthesis are:· oxygen (O2) · glucose (C6H12O6)

Photosynthesis produces the glucose that feeds respiration, and eventually, all of us.

Photosynthesis also produces the oxygen that filled the atmosphere and made complex life, as we know it possible.

Photosynthesis

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Photosynthesis and the addition of oxygen to Earth's atmosphere, began about 2.5 BYA, and was having a major impact by 2.0 BYA.

This is called the Oxygen Catastrophe because it spelled the extinction of a vast number of life forms that were anaerobic and were poisoned by oxygen.

Bacteria that are killed by oxygen are called obligate anaerobes. They survive today, but not when exposed to the atmosphere.

The Oxygen Catastrophe

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This simple equation sums up the result of photosynthesis: its reactants and products.

However, the processes that make photosynthesis possible are not very simple.

Just like the four stages of anaerobic result in a simple equation, the process itself is complicated.

Similarly, the process of photosynthesis is complicated. And in some ways similar to the steps of respiration, but backwards.

Photosynthesis


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During respiration the molecules NAD+ and FAD are used to store energy.

Photosynthesis uses the molecule NADP+, which is a lot like NAD+, to store energy, and convey it between its two stages.

The reduced form of NADP+ is NADPH.

NADPH

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There are two forms of photosynthesis. Both forms are still used, but the first form, Cyclic Energy Transport, is probably of earliest origin. And is not nearly as productive.

It does not create glucose, it just converts solar energy to ATP. It is probably one of the earliest sources of energy for cells.

Cyclic Energy Transport

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It still operates in cells when there is too little NADP+ available to create glucose. It uses only Photosystem I (which you'll learn about soon).

It is very analogous to anaerobic respiration (which yields 2 ATP) versus aerobic respiration (which yields 36-38 ATP).

It is older and less productive but still used. That's all you need to know about this Cyclic Energy Transport.

Cyclic Energy Transport

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45 When the oxygen catastrophe occurred, which type of organisms died?

A aerobic

B anaerobic

C facultative bacteria

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46 What are the product(s) of cyclic energy transport?

A glucose

B ATP

C glucose and ATP

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Noncyclic Energy Transport creates glucose and oxygen: it's a much more important process.

And if Cyclic Energy Transport is like anaerobic respiration. Noncyclic Energy Transport is a lot like aerobic respiration.

Noncyclic Energy Transport

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There are two major stages to Noncyclic Energy Transport:

Light Dependent Reactions

Light Independent Reactions

Noncyclic Energy Transport

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Light Dependent Reactions occur in membrane bound structures called thylakoids.

It's necessary to have a membrane surface separating the inside from the outside on an enclosed volume, thylakoids provide that. The inside is called the lumen; the outside is called the stroma.

Light Dependent Reactions

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ThylakoidThis shows the membrane, separating the stroma from the lumen, the two photosystems and the enzymes, ATP Synthase and NADP Reductase.

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The light reactions will use Photosystem II and Photosystem I to create an excess of protons in the stroma, and a deficit in the lumen.

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The light reactions will use Photosystem II and Photosystem I to create an excess of protons in the stroma, and a deficit in the lumen.

The only way protons can get back to the lumen, is through ATP Synthase, to produce ATP.

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Photosystems I and II depend on a chlorophyll, a molecule that absorbs red and violet-blue light and uses it to energize electrons to a higher energy level.

Chlorophyll

Chlorophyll gives plants their green color.

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Photosystems I and II

Photosystem II Photosystem Ichlorophyll

Those are used to pump protons out of the lumen, creating an electrical potential difference which is used, with ATP Synthase, to create ATP.

First, Photosystem II (they were named in the order of discovery) absorbs light and energizes electrons.

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chlorophyll

Then, Photosystem I absorbs more light and re-energizes those electrons. Those are used to store energy by using NADP Reductase to reduce NADP+ to NADPH (adding electrons to NADP+).


Photosystem II Photosystem I

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chlorophyll

Photosystem II Photosystem I


The ATP and NADPH are then sent to the Light Independent Reaction, the Calvin Cycle.

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This is sometimes called the Dark Reaction, but that's not accurate since it takes place in the light or the dark: it's independent of light.

It takes the ATP and NADPH produced in the light cycle and uses them to convert CO2 and H2O into Glucose (C6H12O6) and O2 in a multi step process.

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In each turn of the cycle the carbon of a CO2 molecule is added to a sugar, releasing O2.

This process captures carbon and releases oxygen. This is the process that drove the Oxygen Catastrophe, flooding Earth's atmosphere with oxygen, while reducing the carbon dioxide, a greenhouse gas, in the atmosphere. This was first performed by cyanobacteria.

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The Calvin Cycle uses solar energy to create glucose.

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This shows the result of 3 turns of the cycle: 3 CO2 are used to create 1 3-carbon sugar.

Glucose requires 2 3-carbon sugars, so 6 turns of the cycle.

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In 3 turns of the cycle we use9 ATP

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In 3 turns of the cycle we use9 ATPand 6 NADPH

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and 3 CO2

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and 3 CO2

to make 1 3-carbon sugar

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The Carbon Cycle

The Calvin Cycle is also called Carbon Fixing.

This means that carbon, a gas in the atmosphere, in the form of CO2, is turned into a solid as a glucose. When glucose is used in respiration, that carbon is then released back into the atmosphere.

This process of fixing and releasing carbon is called the Carbon Cycle. Carbon is not being created or destroyed, but cycles through the environment.

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47 The inside of the thylakoid is called the ______ and the outside is called the ______.

A lumen, stroma

B stroma, lumen

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48 The Calvin Cycle takes place in the_______.

A dark

B light

C dark or the light

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49 Oxygen is released during the _______.

A Light-dependent reaction

B Light-independent reaction

C All of the above

D None of the above

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50 The light-dependent reactions form _____ and _____.

A ATP and glucose

B glucose and water

C CO2 and O2

D ATP and NADPH

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51 Another term for forming sugar from CO2 is:

A carbon fixing

B hydrolysis

C respiration

D sweetening

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Global Climate Change

The carbon cycle plays a key role in Global Climate Change.

Photosynthesis releases oxygen into the air, but also takes CO2 out of the air.

CO2 is a greenhouse gas, it absorbs infrared light that would otherwise carry heat away from Earth, into space; cooling Earth.

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If it were not for CO2, and other greenhouse gases, Earth would be far colder, perhaps too cold to support life as we know it.

Greenhouse gases are essential for life.

However, the amount of greenhouse gases in Earth's atmosphere is critical to maintaining a constant average temperature for the planet.

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A great deal of carbon was trapped under the surface of Earth by life forms that died over many millions of year; effectively taking that carbon out of the carbon cycle.

That reduced the CO2 in the atmosphere, reducing the temperature of Earth by allowing more heat to leave, leading to our current temperature.

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The hydrocarbons we use for energy (oil and natural gas) were formed from the breakdown of that long-dead plant and animal life.

As we burn those fuels, we are releasing CO2 back into the atmosphere, increasing the greenhouse gases in the atmosphere.

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As a result, more heat is being trapped in our atmosphere; the balance of energy brought to Earth by solar energy, and released from Earth in infrared radiation is being changed.

This is causing Earth's average temperature to rise.

The effect of this temperature rise is not that the temperature goes up in all places or in all years necessarily.

But it is projected that there will be massive changes in climate in the future, with accompanying changes in sea level, crops, plant and animal life, etc.

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52 Greenhouses gases are dangerous and should be reduced as much as possible.

True

False

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53 Carbon was used from the carbon cycle, reducing CO2 in the air, as __________.

A the amount of life on Earth decreased

B as animals died and were buried under earth

C fermentation began

D All of the above

E None of the above

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54 A very warm winter in New Jersey this year would indicate that global climate change is occurring.

True

False

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55 A very cold winter in New Jersey this year would indicate that global climate change is occurring.

True

False

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