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Biology 112 > Lecture 11: Citric Acid Cycle, ETC and Fermentation > Flashcards

Lecture 11: Citric Acid Cycle, ETC and Fermentation Flashcards

1
Q

Where does pyruvate oxidation occur?

A

Mitochondria

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2
Q

What is pyruvate oxidation coupled with?

A

The reduction of NAD+ to NADH

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3
Q

The half-reactions produce a lot of energy, what is this energy used for?

A

To generate a covalent bond to coenzyme A

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4
Q

What is the final product of pyruvate oxidation?

A

2 molecules of acetyl coenzyme A

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5
Q

Where do the acetyl coenzyme A’s go after pyruvate oxidation?

A

Citric Acid Cycle

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6
Q

Where does the citric acid cycle occur?

A

Mitochondria

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7
Q

What does dehydrogenase do?

A

Catalyzes redox reactions

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8
Q

What are the products of the citric acid cycle?

A
  • 3 NADH
  • 1 FADH2
  • 1 GTP = 1 ATP
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9
Q

Why does one step reduce FAD instead of NAD+ ?

A

-FAD has a higher redox potential meaning that the electrons are more likely to flow there away from NAD+
-If FAD was not there the cycle would go in the opposite direction and would be useless

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10
Q

What is the main function of the ETC?

A

Converts NADH and FADH2 molecules back to NAD+
- Shuttles electrons to oxygen

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11
Q

Where does the ETC occur?

A

In the Christae of the mitochondria

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12
Q

How does complex I work?

A
  1. NADH binds to the first complex and gives up its two electrons
  2. There is a cofactor bound to the enzyme that gets reduced. This reaction releases enough energy to cause a conformational change of complex I.
  3. The energy results in the transport of a proton across the inner mitochondrial membrane against the concentration gradient.
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13
Q

What does ubiquinone do in the ETC?

A

-The electron from the oxidation of NADH is transferred via ubiquinone to complex III.
-Ubiquinone gets reduced by taking up the electron and a proton at the same time.

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14
Q

Why can ubiquinone pass laterally through the plasma membrane?

A

-Ubiquinone is hydrophobic

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15
Q

True or False: There are binding sites for ubiquinone outside of complex I and complex III

A

False , there is one outside of complex I but the one for complex III is on the inside

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16
Q

How does complex III work?

A

Ubiquinone binds to complex III then it gets oxidized and the proton goes across the concentration gradient again through complex III and the electron is passed on.

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17
Q

Why does FADH2 need to be oxidized at a unique protein complex?

A

FADH2 carries less energy than NADH which is why it must be oxidized at it unique protein complex, complex II.
-Cannot use complex I because it transfers one less proton across the gradient.

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18
Q

How does complex II work?

A

-Electrons enter complex II via oxidation of FADH2.
-Electrons are then used to reduce ubiquinone and are then transferred to complex III

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19
Q

Does complex II have a protein pump?

A

No

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20
Q

What is cytochrome C?

A

Hydrophobic protein found between complexes III and IV

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21
Q

What does cytochrome C do?

A

Transports electrons from complex III to complex IV

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22
Q

How does complex IV work? (not including oxygen part)

A

-Complex IV is reduced by cytochrome C resulting in a conformational change leading to a release of energy and protons being transported across the membrane

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23
Q

How does complex IV work? (including oxygen)

A

-A cofactor and heme group hold an oxygen molecule tight, in position for complex IV to reduce it with electrons
-The O2 is then reduced to produce H2O

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24
Q

What are heme groups?

A

Iron or copper atoms

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25
Q

How does cyanide cause death?

A

Cyanide can bind irreversibly(covalently) to a heme group preventing oxygen from being reduced which leads to death by suffocation

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26
Q

What is the electrochemical proton gradient?

A

Gradient that is electric(charge difference), chemical gradient(more protons one side than the other), there is a pH difference and voltage difference they generate what is called an electromotive force.

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27
Q

What is electromotive force?

A

When protons really want to flow from high concentration to low concentration , however they can’t due to them being ions

28
Q

What uses the electromotive force?

A

ATP Synthase

29
Q

What is ATP Synthase?(not how it works)

A

Protein Complex

30
Q

How does ATP Synthase work?

A

As protons enter the ATP synthase they release energy which drives the ATP synthase to spin and forces an ADP molecule to collide with an inorganic phosphate molecule.

31
Q

How many protons make one ATP via ATP Synthase?

A

3 protons make 1 ATP molecule

32
Q

Is ATP synthase part of the ETC?

A

No, it is separate

33
Q

How do we know the ATP Synthase is separate?

A

There are bacteria that only have ATP Synthase and no ETC

34
Q

Can ATP Synthase run in reverse? How?

A

Yes it can. It can hydrolyze ATP and pump protons out

35
Q

What happens when the ETC is uncoupled from ATP Synthase? Why would an organism want this?

A

Produces heat. Hibernating animals and newborns need to stay warm

36
Q

How is glycolysis regulated if there is a surplus of ATP?

A

Glycolysis gets regulated down

37
Q

How is the citric acid cycle regulated if there are high concentrations of NADH?

A

Citric Acid Cycle gets regulated down

38
Q

How is the ETC regulated is there is a low proton gradient ?

A

ETC gets regulated up

39
Q

When does fermentation occur?

A

When there is a lack of oxygen

40
Q

What two processes don’t occur during fermentation?

A

-ETC
-Citric Acid Cycle

41
Q

Why does the citric acid cycle shut down if it does not directly require O2?

A

Due to the ETC being shut down no NADH is being oxidized back to NAD+.
The main goal of the citric acid cycle is to create NADH , without the ETC there is a surplus in NADH causing the citric acid cycle to be regulated down

42
Q

What is the only process of aerobic cellular respiration that can occur without oxygen?

A

Glycolysis

43
Q

What are the two types of fermentation?

A
  1. Lactic Acid
  2. Alcohol Fermenation
44
Q

Where does lactic acid fermentation occur?

45
Q

When is a typical time lactic acid fermentation occurs?

A

During heavy exercise muscles run out of oxygen

46
Q

What is the final electron acceptor in lactic acid fermentation ?

47
Q

What occurs during lactic acid fermentation?

A
  1. Pyruvate is reduced
  2. NADH is oxidized
48
Q

What is the oxidized NADH used for after lactic acid fermentation?

A

Used in glycolysis to make ATP

49
Q

Where does lactic acid fermentation not occur?

A

The brain(why you drown fast)

50
Q

What is the end product of lactic acid fermentation

A

-2 lactate molecules

51
Q

Why is lactate very unfavourable?

A

-It is less oxidized than pyruvate

52
Q

What makes people fat?

A

-If you have too much acetyl coA(which is what carbs, fats and lipids are all converted to)
-Your body turns on the anabolic pathway and shuttles some of the acetyl coA out instead of inside the citric acid cycle

53
Q

What is used first when you are starved?

A

Glycogen stored in muscles and the liver are used first

54
Q

What is used second when starved?

A

Fats(but fats must be converted to glucose first)

55
Q

What is the final molecule used when starved?

56
Q

What step of aerobic cellular respiration is glucose completely oxidized to CO2?

A

Citric Acid Cycle

57
Q

How many steps in citric acid cycle are not redox reactions?

58
Q

How many electrons are required to reduce O2?

59
Q

What is the way that ATP is formed through ATP synthase?

A

oxidative level phosphorylation

60
Q

How is the majority of ATP produced?

A

Via oxidative level phosphorylation

61
Q

What is older ATP synthase or the ETC?

A

ATP synthase

62
Q

Does fermentation produce any energy?

A

No it does not because lactate is less favourable than pyruvate

63
Q

What molecule has the highest energy content and why?

A

Fat because it is made up of the most C-H bonds

64
Q

Why are carbohydrates better than sugar?

A

Carbohydrates release glucose slowly

65
Q

Why is snacking and drinking at night bad?

A

Shuts down/Reduces catabolism of stored fat

Biology 112 (24 decks)

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