to do- check it out! this vast website has many short lectures on various aspects of biology. they...
TRANSCRIPT
TO DO- check it out!
• http://www.khanacademy.org/
This vast website has many short lectures on various aspects of Biology. They will help with your understanding of difficult concepts.
HOW CELLS HARVEST CHEMICAL ENERGY(CELLULAR RESPIRATION)
Important points to review….
• Energy is one-way flow.
• Energy is not created or destroyed it can only be converted from one form to another.Solar energy Chemical energy
(sun) (stored in glucose molecule)
Overview Photosynthesis Reaction:
6CO2 + 12 H2O C6H12O6 + 6O2 + 6 H2O
2nd Important Energy Reaction
Overview Cellular Respiration Reaction:
C6H12O6 + 6O2 6CO2 + 6 H2O + (32 ATP)
Cellular respiration is an exergonic process that transfers energy from the bonds in glucose to form ATP.
Photosynthesis and cellular respiration provide energy for life - 4 important points
1.
2.
3.
4.
© 2012 Pearson Education, Inc.
Sunlight energy
ECOSYSTEM
Photosynthesisin chloroplasts
Cellular respirationin mitochondria
(for cellularwork)
Heat energy
GlucoseCO2
H2O O2
ATP
The connection between photosynthesis and cellular respiration
Breathing
Lungs
BloodstreamCO2 O2
O2CO2
Muscle cells carrying outCellular Respiration
Glucose O2 CO2 H2O ATP
The connection between breathing and cellular respiration
Breathing supplies O2 for use in cellular respiration and removes CO2
CONNECTION: The human body uses energy from ATP for all its activities
The average adult human needs about 2,200 kcal (the same as a food Calorie) of energy per day.
– About 75% of these calories are
used to maintain a healthy body.
– The remaining 25% is used to
power physical activities.
Cells tap energy from electrons “falling” from organic fuels to oxygen
The energy necessary for life is contained in the arrangement of electrons in chemical bonds in organic molecules.
An important question is how do cells extract this energy?
– When the carbon-hydrogen bonds of glucose are broken, electrons are transferred to oxygen.
– Oxygen has a strong tendency to attract electrons.
– An electron loses potential energy when it “falls” slowly to oxygen. That energy can be picked up by ATP!
Cells tap energy from electrons “falling” from organic fuels to oxygen
Energy can be released from glucose by simply burning it.
The energy is dissipated as heat and light and is not available to living organisms.
On the other hand, cellular respiration is the controlled breakdown of organic molecules.
Summation: Energy is
– ___________________________________
– ___________________________________
– ___________________________________
Cells tap energy from electrons “falling” from organic fuels to oxygen
The movement of electrons from one molecule to another is an oxidation-reduction reaction, or redox reaction.
Cells tap energy from electrons “falling” from organic fuels (glucose) to oxygen
Enzymes are necessary to oxidize glucose and other foods.
NAD+
– is an important enzyme in oxidizing glucose,
– accepts electrons, and
– becomes reduced to NADH.
Cells tap energy from electrons “falling” from organic fuels to oxygen
There are other electron “carrier” molecules that function like NAD+.
– They form a staircase where the electrons pass from one to the next down the staircase.
– These electron carriers collectively are called the electron transport chain.
– As electrons are transported down the chain, ATP is generated.
Overview: Cellular respiration occurs in three main stages
Cellular respiration consists of a sequence of steps that can be divided into three stages.
– Stage 1 – ______________________
– Stage 2 – ______________ and ___________________
– Stage 3 – ______________________
Mitochondria
Overview: Cellular respiration occurs in three main stages
Stage 1: Glycolysis
Glycolysis harvests chemical energy by oxidizing glucose to pyruvate
In glycolysis,– a single molecule of ____________
is enzymatically cut in half
through a series of steps,– two molecules of _____________
are produced,– two molecules of NAD+
are reduced to two molecules
of ____________, and– a net of two molecules of _________
is produced.
6
1,3-Bisphospho-glycerate
3-Phospho-glycerate
2-Phospho-glycerate
Phosphoenol-pyruvate (PEP)
Pyruvate
NADH NADH
NADNAD
H H
ADP ADP
ADP ADP
ATP ATP
ATP ATP
H2O H2O
P P
P
P P
P
P
P
P
P P
P
P
P
Glycolysis harvests chemical energy by oxidizing glucose to pyruvate
The steps of glycolysis can be grouped into two main phases.
– In steps 1–4, the energy investment phase,
– energy is consumed as two ATP molecules are used to energize a glucose molecule,
– which is then split into two small sugars that are now primed to release energy.
– In steps 5–9, the energy payoff,
– two NADH molecules are produced for each initial glucose molecule and
– 4 ATP molecules are generated. (net gain of 2!)
Glycolysis harvests chemical energy by oxidizing glucose to pyruvate
ATP is formed in glycolysis by substrate-level phosphorylation during which
– an enzyme transfers a ____________ group from a substrate molecule to ADP and
– ATP is formed.
Overview: Cellular respiration occurs in three main stages
Stage 2: The citric acid cycle
Pyruvate is oxidized prior to the citric acid cycle Two molecules of pyruvate are produced for each molecule of glucose
that enters glycolysis.
Pyruvate does not enter the citric acid cycle, but undergoes some chemical grooming in which
– a carboxyl group is removed and given off as _______,
– the two-carbon compound remaining is oxidized while a molecule of NAD+ is reduced to __________,
– coenzyme A joins with the two-carbon group to form acetyl coenzyme A, abbreviated as acetyl CoA, and
– acetyl CoA enters the citric acid cycle.
The citric acid cycle completes the oxidation of organic molecules, generating
many NADH and FADH2 molecules
The citric acid cycle
– is also called the Krebs cycle (after the German-British researcher Hans Krebs, who worked out much of this pathway in the 1930s),
– completes the oxidation of organic molecules (glucose), and
– generates many NADH and FADH2 molecules.
Acetyl CoA
Citric Acid Cycle
CoA
CoA
CO22
3
3
NAD
3 H
NADH
ADPATP P
FAD
FADH2
During the citric acid cycle the two-carbon group of acetyl CoA is added to a four-carbon compound, forming citrate, citrate is degraded back to the four-carbon compound,two CO2 are released, and ___ ATP, ___ NADH, and __-FADH2 are produced.
The citric acid cycle completes the oxidation of organic molecules, generating many
NADH and FADH2 molecules
Remember that the citric acid cycle processes two molecules of acetyl CoA for each initial glucose.
Thus, after two turns of the citric acid cycle, the overall yield per glucose molecule is
– 2 ATP,
– 6 NADH, and
– 2 FADH2.
NADH
NADH
NAD
NAD
NADNADH
H
H
H
CO2
CO2
ATP
ADP P
FAD
FADH2
CoA
CoA
321 4 5
34
5
1
2
Acetyl CoA
Oxaloacetate
Citric Acid Cycle
2 carbons enter cycle
Citrate
leaves cycle
Alpha-ketoglutarate
leaves cycle
Succinate
Malate
StepAcetyl CoA stokesthe furnace.
Steps –NADH, ATP, and CO2
are generated during redox reactions.
Steps –Further redox reactions generateFADH2 and more NADH.
Overview: Cellular respiration occurs in three main stages
Stage 3: Oxidative phosphorylation Use _____________ and __________ already formed
in previous stages Produce ___ ___ ___
Most ATP production occurs by oxidative phosphorylation
Electrons from NADH and FADH2 travel down the electron transport chain to ______.
Oxygen picks up H+ to form water.
Energy released by these redox reactions is used to pump H+ from the mitochondrial matrix into the intermembrane space.
In __________________, the H+ diffuses back across the inner membrane through ________________complexes, driving the synthesis of ATP.
Oxidative Phosphorylation
Electron Transport Chain Chemiosmosis
Mito-chondrialmatrix
Inner mito-chondrialmembrane
Intermem-branespace
Electronflow
Proteincomplexof electroncarriers
Mobileelectroncarriers
ATPsynthase
NADH NAD 2 H
FADH2FAD
O2H2O
ADP P ATP
12
H
H
H
H
H
H
H
H
H
H
H
I
II
IIIIV
Review: Each molecule of glucose yields many molecules of ATP
Recall that the energy payoff of cellular respiration involves– glycolysis,– alteration of pyruvate,– the citric acid cycle, and– oxidative phosphorylation.
The total yield is about 32 ATP molecules per glucose molecule.
This is about 34% of the potential energy of a glucose molecule.
In addition to the ATP, _______and _______are produced.
NADH
FADH2
NADH FADH2NADH
orNADH
MitochondrionCYTOPLASM
Electron shuttlesacross membrane
Glycolysis
Glucose2
Pyruvate
PyruvateOxidation2 Acetyl
CoA
Citric AcidCycle
OxidativePhosphorylation
(electron transportand chemiosmosis)
Maximumper glucose:
by substrate-levelphosphorylation
by substrate-levelphosphorylation
by oxidativephosphorylation
2
2
2
2
6 2
ATP 2 about
28 ATP AboutATP32
ATP 2
http://Cellular Respiration Animation
Watch it until it makes sense!
Glycolysis - Fermentation Animation
Fermentation enables cells to produce ATP without oxygen
Fermentation is a way of harvesting chemical energy that does not require oxygen. Fermentation
– takes advantage of glycolysis….so..
– produces _____ ATP molecules per glucose, and
– reduces NAD+ to _________.
The trick of fermentation is to provide an anaerobic path for recycling NADH back to NAD+.
Animation: Fermentation OverviewRight click on animation / Click play
Your muscle cells and certain bacteria can oxidize NADH through lactic acid fermentation, in whichNADH is oxidized to NAD+ andpyruvate is reduced to lactate.
The baking and winemaking industries have used alcohol fermentation for thousands of years.
In this process yeasts (single-celled fungi)oxidize NADH back to NAD+ and convert pyruvate to CO2 and ethanol.
EVOLUTION CONNECTION: Glycolysis evolved early in the history of life on Earth
Glycolysis is the universal energy-harvesting process of life.
The role of glycolysis in fermentation and respiration dates back to
– life long before oxygen was present,
– when only prokaryotes inhabited the Earth,
– about 3.5 billion years ago.
The ancient history of glycolysis is supported by its
– occurrence in all the domains of life and
– location within the cell, using pathways that do not involve any membrane-bounded organelles.
Cells use many kinds of organic molecules as fuel for cellular respiration
Although glucose is considered to be the primary source of sugar for respiration and fermentation, ATP is generated using
– carbohydrates,
– fats, and
– proteins.
© 2012 Pearson Education, Inc.
Food, such aspeanuts
Sugars Glycerol Fatty acids Amino acids
Aminogroups
OxidativePhosphorylation
CitricAcidCycle
PyruvateOxidation
Acetyl CoA
ATP
Glucose G3P PyruvateGlycolysis
Carbohydrates Fats Proteins
Food molecules provide raw materials for biosynthesis
Cells use intermediates from cellular respiration for the biosynthesis of other organic molecules.
You should now be able to
1. Compare the processes and locations of cellular respiration and photosynthesis.
2. Explain how breathing and cellular respiration are related.
3. Provide the overall chemical equation for cellular respiration.
4. Explain how the human body uses its daily supply of ATP.
You should now be able to
5. Explain how the energy in a glucose molecule is released during cellular respiration.
6. Describe the general roles of dehydrogenase, NADH, and the electron transport chain in cellular respiration.
7. Compare the reactants, products, and energy yield of the three stages of cellular respiration.
You should now be able to
9. Compare the reactants, products, and energy yield of alcohol and lactic acid fermentation.
10. Briefly explain how carbohydrates, fats, and proteins are used as fuel for cellular respiration.
Aerobic respiration……an animation to help you visualize
http://www2.nl.edu/jste/aerobic_respiration.htm
cellular work
chemiosmosis
H gradient
glucose andorganic fuels
Cellularrespiration
generates has three stages oxidizes
uses
producesome
producesmany
to pullelectrons down
H diffusethrough
ATP synthase
pumps H to createuses
usesby a process called
energy for
(a)
(b)
(c)
(d)
(e)
(f)
(g)
to
Proton Pump/Chemiosmosis
AN OVERVIEW OF AEROBIC RESPIRATION
