Cell Respiration and Fermentation (Ch. 9) Flashcards
(69 cards)
1
Q
Describe the energy flow and chemical recycling in ecosystems at a high level.
A
2
Q
What is fermentation? (high-level answer)
A
Fermentation is a partial degradation of sugars or other organic fuel that occurs without oxygen. It is less prevalent and efficient than aerobic respiration.
3
Q
What is aerobic respiration? (high-level answer)
A
Aerobic respiration is a catabolic pathway in which oxygen is consumed along with organic fuel. It is more prevalent and efficient than fermentation.
organic compounds + oxygen —> carbon dioxide + water + energy
Like the combustion of gasoline…
4
Q
What organisms’ cells use aerobic respiration?
A
The cells of most eukaryotic and many prokaryotic organisms. Some prokaryotes use substances other than oxygen as reactants – this is anaerobic respiration.
5
Q
What is the overall equation for the degradation of glucose?
A
C6H12O6 + 6 O2 ——> 6 CO2 + 6 H2O + Energy (ATP + heat)
∆G = -686 kcal/mol (2870 kJ) … exergonic
6
Q
Do redox reactions always involve the complete transfer of electrons from one compound to another? Give an example of why or why not.
A
No, they do not. Sometimes, they can create energy from changing the degree of sharing in covalent bonds.
Ex.: In methane combustion, the electrons lose potential energy to the surroundings because they end up being shared unequally.
7
Q
Consider the summary equation for cell respiration as a redox process. WHat is oxidized and what is reduced?
A
Glucose is oxidized (to CO2) and O2 is reduced (to H2O)
The fuel is oxidized and the oxygen is reduced.
8
Q
Why are organic molecules with lots of hydrogen good fuels?
A
They contain many “hilltop” electrons. All those bonds with H have electrons whose energy can be released as they fall down an energy gradient when they are transferred to oxygen.
9
Q
What is NAD+? Why is it good for its purpose?
Is it an oxidizing or reducing agent in respiration?
A
NAD+ (nicotinamide adenine dinucleotide) is a coenzyme that is an electron carrier. It carries electrons with protons (i.e. hydrogen atoms). It is good for this because it can cycle between oxidized (NAD+) and reduced (NADH) states easily.
NAD+ is an oxidizing agent. (Think: it accepts electrons, so it is reduced, so it is an oxidizing agent.)
10
Q
How does NAD+ trap electrons from glucose and other organic molecules?
A
Enzymes called dehydrogenases remove a pair of Hydrogen atoms from the substrate (i.e. glucose), oxidizing it. The enzymes deliver 2 electrons and 1 proton to the coenzyme, NAD+. Other proton is released as an ion into the solution.
11
Q
What is an electron transport chain?
A
An electron transport chain is a number of molecules – mostly proteins – built into the inner membrane of the mitochondria of eukaryotic cells and the plasma membrane of aerobically respiring prokaryotes.
Electrons are removed from glucose and shuttled by NADH to the “top.” Then, at the bottom, lower-energy O2 captures the electrons and the H+, forming water.
Instead of one big, energy-losing step, the electrons cascade down in a series of redox reactions, losing a small amount of energy each step.
12
Q
What are the three metabolic stages of harvesting energy from glucose by cellular respiration?
A
13
Q
What is glycolysis?
A
Glycolysis begins the degradation process by breaking glucose into two molecules of pyruvate.
14
Q
Where does glycolysis happen?
A
Glycolysis happens in the cytosol.
15
Q
In eukaryotes, where does pyruvate go after glycolysis and what happens to it?
A
Pyruvate enters the mitochondrion and is oxidized (loses electrons) to a compound called acetyl CoA.
16
Q
Where is pyruvate oxidized to acetyl CoA?
A
The mitochondrion.
17
Q
Is pyruvate reduced or oxidized into acetyl CoA?
A
oxidized
18
Q
What does acetyl CoA do after it becomes that (from pyruvate)
A
It enters the citric acid cycle.
19
Q
What does the citric acid cycle do?
A
The citric acid cycle completes the breakdown of glucose to carbon dioxide.
20
Q
Where do pyruvate –> acetyl CoA and the citric acid cycle take place in prokaryotes?
A
In the cytosol
21
Q
What happens in the third step of cellular respiration?
A
The electron transport chain accepts electrons from the breakdown products of the first two stages (usually via NADH) and passes these electrons from one molecule to another.
At end: electrons combine with H+ and molecular oxygen to form water
22
Q
What process does the mitochondrion use to synthesize ATP using energy from cell respiration? Why is it called that?
A
oxidative phosphorylation. It is called that because it is powered by redox reactions of the electron transport chain.
23
Q
What are the two processes of oxidative phosphorylation? Where do they happen?
A
Electron transport and chemiosmosis. In eukaryotes, they happen at the inner membrane of the mitochondrion.
24
Q
Oxidative phosphorylation accounts for 90% of ATP generated by respiration. What does the rest? How does it work?
A
Substrate-level phosphorylation.
An enzyme transfers a phosphate group from a substrate molecule to ADP rather than adding an inorganic phosphate molecule to ADP.
25
Give a high-level overview of cell respiration
1. Glycolysis breaks down glucose into pyruvate in the cytosol.
2. In the mitochondrion, pyruvate is oxidized into acetyl CoA
3. The citric acid cycle takes the acetyl CoA and oxidizes it more into CO2.
4. Then odidative phosphorylation:
1. electron transport chains convert chemical energy into a form used for...
2. ATP synthesis in chemiosmosis
26
What are the two phases of glycolysis? What is the net energy yield?
Energy investment
Energy payoff
net energy yield: 2 ATP + 2 NADH
27
What is step 1 of the glycolysis energy investment phase?
Steps of the **glycolysis energy investment phase**:
Start with glucose
1. **Hexokinase transfers a phosphate group from ATP to glucose, making it more chemically reactive. The charge on the phosphate traps the sugar in the cell. *_Starts with*_: Glucose. _*Ends with_*: Glucose 6-phosphate**
2. Glucose 6-phosphate is converted to its isomer, fructose 6-phosphate. *_Starts with*_: Glucose 6-phosphate. _*Ends with_*: Fructose 6-phosphate
3. Phosphofructokinase transfers a phosphate group from ATP to the opposite end of the sugar, investing a second molecule of ATP. *_Starts with:_* Fructose 6-phosphate. *_Ends with_*: Fructose 1,6-bisphosphate
4. Aldolase cleaves the sugar molecule into two different three-carbon sugars (isomers). *_Starts with:_* Fructose 1,6-bisphosphate. *_Ends with_*: Dihydroxyacetone phosphate and Glyceraldehyde 3-phosphate
5. Isomerase catalyzes the reversible conversion between the two isomers. This reaction never reaches equilibrium: Glyceraldehyde 3-phosphate is used as the substrate of the next reaction (step 6) as fast as it forms). *_Starts with:*_ Dihydroxyacetone phosphate and Glyceraldehyde 3-phosphate _*Ends with:_* Dihydroxyacetone phosphate and Glyceraldehyde 3-phosphate
28
What is step 2 of the glycolysis energy investment phase?
Steps of the **glycolysis energy investment phase**:
Start with glucose
1. Hexokinase transfers a phosphate group from ATP to glucose, making it more chemically reactive. The charge on the phosphate traps the sugar in the cell. *_Starts with*_: Glucose. _*Ends with_*: Glucose 6-phosphate
2. **Glucose 6-phosphate is converted to its isomer, fructose 6-phosphate. *_Starts with*_: Glucose 6-phosphate. _*Ends with_*: Fructose 6-phosphate**
3. Phosphofructokinase transfers a phosphate group from ATP to the opposite end of the sugar, investing a second molecule of ATP. *_Starts with:_* Fructose 6-phosphate. *_Ends with_*: Fructose 1,6-bisphosphate
4. Aldolase cleaves the sugar molecule into two different three-carbon sugars (isomers). *_Starts with:_* Fructose 1,6-bisphosphate. *_Ends with_*: Dihydroxyacetone phosphate and Glyceraldehyde 3-phosphate
5. Isomerase catalyzes the reversible conversion between the two isomers. This reaction never reaches equilibrium: Glyceraldehyde 3-phosphate is used as the substrate of the next reaction (step 6) as fast as it forms). *_Starts with:*_ Dihydroxyacetone phosphate and Glyceraldehyde 3-phosphate _*Ends with:_* Dihydroxyacetone phosphate and Glyceraldehyde 3-phosphate
29
What is step 3 of the glycolysis energy investment phase?
Steps of the **glycolysis energy investment phase**:
Start with glucose
1. Hexokinase transfers a phosphate group from ATP to glucose, making it more chemically reactive. The charge on the phosphate traps the sugar in the cell. *_Starts with*_: Glucose. _*Ends with_*: Glucose 6-phosphate
2. Glucose 6-phosphate is converted to its isomer, fructose 6-phosphate. *_Starts with*_: Glucose 6-phosphate. _*Ends with_*: Fructose 6-phosphate
3. **Phosphofructokinase transfers a phosphate group from ATP to the opposite end of the sugar, investing a second molecule of ATP. *_Starts with:_* Fructose 6-phosphate. *_Ends with_*: Fructose 1,6-bisphosphate**
4. Aldolase cleaves the sugar molecule into two different three-carbon sugars (isomers). *_Starts with:_* Fructose 1,6-bisphosphate. *_Ends with_*: Dihydroxyacetone phosphate and Glyceraldehyde 3-phosphate
5. Isomerase catalyzes the reversible conversion between the two isomers. This reaction never reaches equilibrium: Glyceraldehyde 3-phosphate is used as the substrate of the next reaction (step 6) as fast as it forms). *_Starts with:*_ Dihydroxyacetone phosphate and Glyceraldehyde 3-phosphate _*Ends with:_* Dihydroxyacetone phosphate and Glyceraldehyde 3-phosphate
30
What is step 4 of the glycolysis energy investment phase?
Steps of the **glycolysis energy investment phase**:
Start with glucose
1. Hexokinase transfers a phosphate group from ATP to glucose, making it more chemically reactive. The charge on the phosphate traps the sugar in the cell. *_Starts with*_: Glucose. _*Ends with_*: Glucose 6-phosphate
2. Glucose 6-phosphate is converted to its isomer, fructose 6-phosphate. *_Starts with*_: Glucose 6-phosphate. _*Ends with_*: Fructose 6-phosphate
3. Phosphofructokinase transfers a phosphate group from ATP to the opposite end of the sugar, investing a second molecule of ATP. *_Starts with:_* Fructose 6-phosphate. *_Ends with_*: Fructose 1,6-bisphosphate
4. **Aldolase cleaves the sugar molecule into two different three-carbon sugars (isomers). *_Starts with:_* Fructose 1,6-bisphosphate. *_Ends with_*: Dihydroxyacetone phosphate and Glyceraldehyde 3-phosphate**
5. Isomerase catalyzes the reversible conversion between the two isomers. This reaction never reaches equilibrium: Glyceraldehyde 3-phosphate is used as the substrate of the next reaction (step 6) as fast as it forms). *_Starts with:*_ Dihydroxyacetone phosphate and Glyceraldehyde 3-phosphate _*Ends with:_* Dihydroxyacetone phosphate and Glyceraldehyde 3-phosphate
31
What is step 5 of the energy investment part of glycolysis?
Steps of the **glycolysis energy investment phase**:
Start with glucose
1. Hexokinase transfers a phosphate group from ATP to glucose, making it more chemically reactive. The charge on the phosphate traps the sugar in the cell. *_Starts with*_: Glucose. _*Ends with_*: Glucose 6-phosphate
2. Glucose 6-phosphate is converted to its isomer, fructose 6-phosphate. *_Starts with*_: Glucose 6-phosphate. _*Ends with_*: Fructose 6-phosphate
3. Phosphofructokinase transfers a phosphate group from ATP to the opposite end of the sugar, investing a second molecule of ATP. *_Starts with:_* Fructose 6-phosphate. *_Ends with_*: Fructose 1,6-bisphosphate
4. Aldolase cleaves the sugar molecule into two different three-carbon sugars (isomers). *_Starts with:_* Fructose 1,6-bisphosphate. *_Ends with_*: Dihydroxyacetone phosphate and Glyceraldehyde 3-phosphate
5. **Isomerase catalyzes the reversible conversion between the two isomers. This reaction never reaches equilibrium: Glyceraldehyde 3-phosphate is used as the substrate of the next reaction (step 6) as fast as it forms). *_Starts with:*_ Dihydroxyacetone phosphate and Glyceraldehyde 3-phosphate _*Ends with:_* Dihydroxyacetone phosphate and Glyceraldehyde 3-phosphate**
32
What are all the steps of the energy investment phase of glycolysis?
Steps of the **glycolysis energy investment phase**:
Start with glucose
1. Hexokinase transfers a phosphate group from ATP to glucose, making it more chemically reactive. The charge on the phosphate traps the sugar in the cell. *_Starts with*_: Glucose. _*Ends with_*: Glucose 6-phosphate
2. Glucose 6-phosphate is converted to its isomer, fructose 6-phosphate. *_Starts with*_: Glucose 6-phosphate. _*Ends with_*: Fructose 6-phosphate
3. Phosphofructokinase transfers a phosphate group from ATP to the opposite end of the sugar, investing a second molecule of ATP. *_Starts with:_* Fructose 6-phosphate. *_Ends with_*: Fructose 1,6-bisphosphate
4. Aldolase cleaves the sugar molecule into two different three-carbon sugars (isomers). *_Starts with:_* Fructose 1,6-bisphosphate. *_Ends with_*: Dihydroxyacetone phosphate and Glyceraldehyde 3-phosphate
5. Isomerase catalyzes the reversible conversion between the two isomers. This reaction never reaches equilibrium: Glyceraldehyde 3-phosphate is used as the substrate of the next reaction (step 6) as fast as it forms). *_Starts with:*_ Dihydroxyacetone phosphate and Glyceraldehyde 3-phosphate _*Ends with:_* Dihydroxyacetone phosphate and Glyceraldehyde 3-phosphate
33
What is step 6 of glycolysis -- the first step of the energy payoff phase?
The five steps of the glycolysis energy payoff phase:
Start with Glyceraldehyde 3-phosphate (one of the two 3-carbon sugars formed.
**6. *_Starts with*_ Glyceraldehyde 3-phosphate; _*ends with_* 1,3-Bisphosphoglycerate. Also yields 2 NADH**
**_Triose phosphate_ dehydrogenase catalyzes two reactions: first, sugar is oxidized by transferring electrons to NAD+, forming NADH. second, energy released from this redox reaction attaches a phosphate group to the oxidized substrate. Product has very high potential energy.**
7. *_Starts with*_ 1,3,bisphosphoclycerate; _*ends with_* 3-phosphoclycerate
The phosphate group added in the last step is transferred to ADP via substrate-level phosphorylation. The carbonyl group of a sugar has been oxidized to the carboxyl (--COO-) of an organic acid (3-phosphoclycerate)
8. *_Starts with_* 3-Phosphoglycerate; *_ends with:_* 2-Phosphoglycerate
The enzyme Phophoglyceromutase relocates the remaining phosphate group
9. *_Starts with_* 2-Phosphglycerate; *_ends with_*: Phosphoenolpyruvate (PEP)
Enolase causes a double bond to form in the substrate by extracting a water molecule, yielding PEP , a compound with very high potential energy
10. *_Starts with_* PEP; *_ends with_* Pyruvate
Pyruvate kinase transfers PEP's phosphate group to ADP (a second example of substrate-level phosphorylation), forming pyruvate.
34
What is step 7 of glycolysis - the second step of the energy payoff phase?
The five steps of the glycolysis energy payoff phase:
Start with Glyceraldehyde 3-phosphate (one of the two 3-carbon sugars formed.
6. *_Starts with*_ Glyceraldehyde 3-phosphate; _*ends with_* 1,3-Bisphosphoglycerate. Also yields 2 NADH
_Triose phosphate_ dehydrogenase catalyzes two reactions: first, sugar is oxidized by transferring electrons to NAD+, forming NADH. second, energy released from this redox reaction attaches a phosphate group to the oxidized substrate. Product has very high potential energy.
**7. *_Starts with*_ 1,3,bisphosphoclycerate; _*ends with_* 3-phosphoclycerate**
**The phosphate group added in the last step is transferred to ADP via substrate-level phosphorylation. The carbonyl group of a sugar has been oxidized to the carboxyl (--COO-) of an organic acid (3-phosphoclycerate)**
8. *_Starts with_* 3-Phosphoglycerate; *_ends with:_* 2-Phosphoglycerate
The enzyme Phophoglyceromutase relocates the remaining phosphate group
9. *_Starts with_* 2-Phosphglycerate; *_ends with_*: Phosphoenolpyruvate (PEP)
Enolase causes a double bond to form in the substrate by extracting a water molecule, yielding PEP , a compound with very high potential energy
10. *_Starts with_* PEP; *_ends with_* Pyruvate
Pyruvate kinase transfers PEP's phosphate group to ADP (a second example of substrate-level phosphorylation), forming pyruvate.
35
What is step 8 of glycolysis - the third step of the energy payoff phase?
The five steps of the glycolysis energy payoff phase:
Start with Glyceraldehyde 3-phosphate (one of the two 3-carbon sugars formed.
6. *_Starts with*_ Glyceraldehyde 3-phosphate; _*ends with_* 1,3-Bisphosphoglycerate. Also yields 2 NADH
_Triose phosphate_ dehydrogenase catalyzes two reactions: first, sugar is oxidized by transferring electrons to NAD+, forming NADH. second, energy released from this redox reaction attaches a phosphate group to the oxidized substrate. Product has very high potential energy.
7. *_Starts with*_ 1,3,bisphosphoclycerate; _*ends with_* 3-phosphoclycerate
The phosphate group added in the last step is transferred to ADP via substrate-level phosphorylation. The carbonyl group of a sugar has been oxidized to the carboxyl (--COO-) of an organic acid (3-phosphoclycerate)
**8. *_Starts with_* 3-Phosphoglycerate; *_ends with:_* 2-Phosphoglycerate**
**The enzyme Phophoglyceromutase relocates the remaining phosphate group**
9. *_Starts with_* 2-Phosphglycerate; *_ends with_*: Phosphoenolpyruvate (PEP)
Enolase causes a double bond to form in the substrate by extracting a water molecule, yielding PEP , a compound with very high potential energy
10. *_Starts with_* PEP; *_ends with_* Pyruvate
Pyruvate kinase transfers PEP's phosphate group to ADP (a second example of substrate-level phosphorylation), forming pyruvate.
36
What is step 9 of glycolysis - the fourth step of the energy payoff phase?
The five steps of the glycolysis energy payoff phase:
Start with Glyceraldehyde 3-phosphate (one of the two 3-carbon sugars formed.
6. *_Starts with*_ Glyceraldehyde 3-phosphate; _*ends with_* 1,3-Bisphosphoglycerate. Also yields 2 NADH
_Triose phosphate_ dehydrogenase catalyzes two reactions: first, sugar is oxidized by transferring electrons to NAD+, forming NADH. second, energy released from this redox reaction attaches a phosphate group to the oxidized substrate. Product has very high potential energy.
7. *_Starts with*_ 1,3,bisphosphoclycerate; _*ends with_* 3-phosphoclycerate
The phosphate group added in the last step is transferred to ADP via substrate-level phosphorylation. The carbonyl group of a sugar has been oxidized to the carboxyl (--COO-) of an organic acid (3-phosphoclycerate)
8. *_Starts with_* 3-Phosphoglycerate; *_ends with:_* 2-Phosphoglycerate
The enzyme Phophoglyceromutase relocates the remaining phosphate group
**9. *_Starts with_* 2-Phosphglycerate; *_ends with_*: Phosphoenolpyruvate (PEP)**
**Enolase causes a double bond to form in the substrate by extracting a water molecule, yielding PEP , a compound with very high potential energy**
10. *_Starts with_* PEP; *_ends with_* Pyruvate
Pyruvate kinase transfers PEP's phosphate group to ADP (a second example of substrate-level phosphorylation), forming pyruvate.
37
What is step 10 of glycolysis - the final step of the energy payoff phase?
The five steps of the glycolysis energy payoff phase:
Start with Glyceraldehyde 3-phosphate (one of the two 3-carbon sugars formed.
6. *_Starts with*_ Glyceraldehyde 3-phosphate; _*ends with_* 1,3-Bisphosphoglycerate. Also yields 2 NADH
_Triose phosphate_ dehydrogenase catalyzes two reactions: first, sugar is oxidized by transferring electrons to NAD+, forming NADH. second, energy released from this redox reaction attaches a phosphate group to the oxidized substrate. Product has very high potential energy.
7. *_Starts with*_ 1,3,bisphosphoclycerate; _*ends with_* 3-phosphoclycerate
The phosphate group added in the last step is transferred to ADP via substrate-level phosphorylation. The carbonyl group of a sugar has been oxidized to the carboxyl (--COO-) of an organic acid (3-phosphoclycerate)
8. *_Starts with_* 3-Phosphoglycerate; *_ends with:_* 2-Phosphoglycerate
The enzyme Phophoglyceromutase relocates the remaining phosphate group
9. *_Starts with_* 2-Phosphglycerate; *_ends with_*: Phosphoenolpyruvate (PEP)
Enolase causes a double bond to form in the substrate by extracting a water molecule, yielding PEP , a compound with very high potential energy
**10. *_Starts with_* PEP; *_ends with_* Pyruvate**
**Pyruvate kinase transfers PEP's phosphate group to ADP (a second example of substrate-level phosphorylation), forming pyruvate.**
38
Summarize glycolysis steps
glucose -\> G6P -\> F6P -\> F16BP -\> [DHAP \<--\> GAP] -\> 3PG -\> 2PG -\> PEP -\> pyruvate
39
What are the important products of glycolysis?
For one glucose...
* 2 ATP (net)
* 2 NADH
* 2 Pyruvate
40
Where does the pyruvate go after glycolysis finishes producing it?
After glycolysis produces pyruvate in the cytosol, the pyruvate goes into the mitochondrion.
41
What does Pyruvate become, how does it become that, and what other products are made?
Pyruvate is oxidized into acetyl CoA, and one NAD+ becomes an NADH in the process. (That means 2 per glucose). Pyruvate oxidation also produces one CO2 in the process. (Again, 2 per glucose)
42
What are the inputs and products of **each turn** of the citric acid cycle?
(multiply by 2 for "per glucose")
input:
* acetyl CoA
outputs:
* 2CO2
* 3 NADH
* 1 ATP (substrate-level phosphorylation)
* 1 FADH2
43
Where does the electron transport chain reside?
The inner membrane of the mitochondrion
44
How, on a high level, does the electron transport chain work?
Electron carriers alternate between reduced and oxidized states as they accept and donate electrons. Each component of the chain becomes reduced when it accepts electrons from its "uphill" neighbor," which is less electronegative. Then it returns to its oxidized form as it passes electrons to its downhill neighbor.
45
In general, what are the electron transport carriers?
FMN, Fe\*S, ubiquinone (Q), cytochromes
46
What is the purpose of the ETC? How much ATP does it produce?
The electron transport chain doesn't make any ATP directly. It eases the fall of electrons from food to oxygen, breaking the large free-energy drop into a series of smaller steps.
47
How does the mitochondrion couple electron transport and energy release to ATP synthesis?
Chemiosmosis
48
What does chemismosis do?
Chemiosmosis takes the energy passed down through ETC and couples it with other reactions to synthesize ATP.
## Footnote
**Chemiosmosis is an energy-coupling mechanism that uses energy stored in the form of an H+ gradient across the mitochondrial membrane to to drive cellular work.**
49
What protein actually makes ATP from ADP and inorganic phosphate?
ATP synthase
50
How does ATP synthase power ATP synthesis? What is this process called?
ATP synthase uses the energy of an existing ion gradient to power ATP synthesis. The ion gradient is [H+] on opposite sides of the inner mitochondrial membrane.
This process is chemiosmosis.
51
What are the four parts of ATP Synthase?
1. Stator
2. Rotor
3. Internal Rod
4. Catalytic knob
52
Describe how ATP synthase works in chemiosmosis
1. H+ ions flowing down gradient enter the stator
2. H+ are bound to the rotor, causing it to spin. After a full turn, the H+ ion goes into the mitochondrial matrix
3. Spinning of the rotor causes an internal rod to spin
4. The turning rod activates catalytic sites on the knob that produce ATP from ADP and inorganic phosphate.
53
In order for ATP synthase to work, must there be a greater [H+] inside the mitochondrion or outside?
Outside. ATP synthase depends on H+ ions exergonically "falling" into the mitochondrion. It uses this coupling to turn the rotor, which turns the internal rod, which turns the catalytic knob, which synthesizes ATP from ADP and D.
54
ATP Synthase needs the mitochondrion to be hypotonic for H+ with respect to the outside of the mitochondrion. Where does that gradient come from?
Certain steps of the electron transport chain release not only an electron but also a proton. The electron carriers are arranged in the inner mitochondrial membrane such that H+ is accepted from the mitochondrial matrix and deposited in the intermembrane space. This gradient is a proton-motive force.
55
About how many ATP are yielded by respiration? Break them down according to source.
* Glycolysis - **2 ATP** from substrate-level phosphorylation
* Citric acid cycle - **2 ATP** (net) from substrate-level phosphorylation
* Oxidative Phosphorylation - **32 ATP**
* 2 NADH yield 4 (2 each) because they cannot cross membrane
* other 8 NADH yield 24 (3 each)
* 2 FADH2 yield 4 (2 each)
**_Total: ~36 ATP_**
56
What would cause oxidative phosphorylation to cases?
If there were no electronegative oxygen to pull electrons down the electron transport chain, OP would cease.
57
What are two ways for certain cells to oxidize organic fuel and generate ATP without oxygen?
1. Anaerobic respiration
2. Fermentation
58
What is the difference between anaerobic respiration and fermentation?
Anaerobic respiration uses an electron transport chain, but fermentation does not.
59
In environments without oxygen, how do organisms' cells use anaerobic respiration?
Their electron transport chains use some other electronegative substance at the end of the chain. Think SO42-. Less electronegative than oxygen, but still electronegative.
60
How does fermentation work without respiratory oxidation? What does it require?
Fermentation is an extension of glycolysis that allows continuous generation of ATP by substrate-level phosphorylation of glycolysis.
It requires enough NAD+ to accept electrons during the oxidation step of glycolysis. That means NADH needs to be recycled into NAD+, or else the process would stop.
**Fermentation = _glycolysis_ + _a mechanism to regenerate NAD+ by transferring electrons from NADH to pyruvate_.**
61
What are the two types of fermentation?
alcohol fermentation and lactic acid fermentation
62
Describe the starting material, products, and mechanism of alcohol fermentation
Pyruvate is converted to ethanol (ethyl alcohol) in two steps:
1. CO2 is released from the pyruvate, which then becomes acetaldehyde (a 2-carbon compound)
2. Acetaldehyde is reduced by NADH to ethanol, regenerating NAD+ and allowing glycolysis to continue.
63
Explain lactic acid fermenation.
Pyruvate is reduced directly by NADH to form lactate as an end product, with no CO2 released.
64
What are key differences between fermentation, anaerobic respiration, and aerobic respiration?
* Different mechanisms for oxidizing NADH back to NAD+:
* fermentation - final e- acceptor is an organic molecule (pyruvate for LAF, acetaldehyde for AF)
* respiration - final e- acceptor at end of ETC is oxygen or another electronegative molecule
* Cell resp yields way more energy; aerobic respiration yields 16 times as much ATP per glucose molecule as does fermentation.
65
What is an obligate anaerobe?
An organism that can only carry out fermentation or anaerobic respiration. Cannot survive with oxygen present.
66
What is a facultative anaerobe?
An organism that can make enough ATP to survive using either fermentation or respiration.
67
How is pyruvate a key juncture in catabolism?
Once glycolysis has oxidized glucose into pyruvate...
O2 PRESENT: aerobic cellular respiration in the mitochondrion
NO O2 PRESENT: Fermentation
68
How can the body process proteins and fats?
* Proteins must be deaminated before being oxidized
* fatty acids of fats undergo beta oxidation to two-carbon fragments and then enter the citric acid cycle as acetyl CoA
69
What mechanism regulates/controls cellular respiration?
Allosteric enzymes at certain points in the respiratory pathway respond to inhibitors/activators.
Example: Phosphofructokinase is stimulated by AMP (an ADP derivative) but is inhibited by ATP and citrate.
