Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biochem 451 Exam 1 > Citric Acid Cycle > Flashcards

Citric Acid Cycle Flashcards

1
Q

What two processes use an enzymatic activity called pyruvate dehydrogenase complex to convert pyruvate from glycolysis to acetyl coA for the citric acid cycle?

A

Oxidative decarboxylation (in higher cells) and non-oxidative decarboxylation (in yeast).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Pyruvate dehydrogenase complex is in what organelle and requires what from the cytoplasm to be transported in?

A

Is in the mitochondrion and requires pyruvate from the cytoplasm.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the names of the three units in the pyruvate dehydrogenase complex?

A

-Pyruvate decarboxylase (E1) -Dihyrolipoamide transacetylase (E2) -Dihyrolipoamide dehydrogenase (E3)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What does the E1 of pyruvate dehydrogenase complex do?

A

It decarboxylates pyruvate, and starts its oxidation (oxidative decarboxylation of pyruvate) using TPP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does E2 of pyruvate dehydrogenase complex do?

A

Oxidation ends in E2 and the reactive molecule (acetyl group) is passed to CoA to make Acetyl CoA using Lipoamide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What does E3 of pyruvate dehydrogenase complex do?

A

handles electrons (via FAD) and regenerates the enzyme (oxidized form of lipoamide).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the five coenzymes used by the pyruvate dehydrogenase complex?

A

-TPP (Thiamine pyrophosphate) -Lipoamide -NAD -FAD -Coenzyme A (also called CoAsh/CoA)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

The reaction catalyzed by pyruvate dehydrogenase complex is similar to what? and why?

A

Similar to alpha-keto-glutarate dehydrogenase complex of citric acid cycle because both involve alpha-keto acids.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe the reaction mech in aerobic higher organisms in pyruvate dehydrogenase complex.

A

-Bind pyruvate by an ionized TPP -decarboxylation -transfer to lipoamide -linkage of acetyl group to CoA/CoASH to form acetyl-CoA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

After acetyl CoA is formed in the reaction mechanism in the pyruvate dehydrogenase complex, what happens to the electrons in the system?

A

-electrons are transferred from the oxidation of FAD (forming FADH2). -electrons are transferred from FADH2 to NAD+ to form NADH and return FADH2 to FAD.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How is the reaction mechanism in pyruvate dehydrogenase complex different in yeast formation?

A

It stops at the decarboxylation step to form acetealdehyde without loss/gain of electrons. There is no reduction/oxidation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What happens to acetealdyhyde is yeast?

A

It is converted to ethanol.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

When oxygen is present in yeast, does fermentation occur?

A

No, activities of E2 and E3 catalyze reactions just like animal cells and produce acetyl CoA.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Where does oxidation mostly occur? What do byproducts of this of oxidation result in?

A

-Mitochondria -Damaged mitochondia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Where does citric acid cycle occur? How many carbons are added from acetyl coA and how many carbons released?

A

-mitochondial matrix -two carbons are added from acetyl CoA and two carbons are released as carbon dioxide.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How many NADH and FADH2 are produced in the citric acid cycle? What other molecule is produced?

A

three NADH and one FADH2 are produced. Another higher energy phosphate (GTP in animals, ATP is plants/bacteria) are produced per acetyl CoA.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

One molecule of glucose yields how many acetyl CoAs for the Citric acid cycle?

A

two acetyl CoAs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

When do the two carbons from acetyl CoA at the beginning of the cycle become oxidized to CO2?

A

Not until the beginning of the second time around the cycle.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the two main parts of the citric acid cycle?

A
  • release of CO2
  • conversion to oxaloacetate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Describe the first part of the beginning of citric acid cycle:

A

-The enzyme citrate synthase catalyzes joining of (4C) oxaloacetate and (2C) acetyl CoA -Makes a activated intermediate (6C) Citryl CoA -Intermediate then becomes (6C) Citrate.

21
Q

Is the first part of the citric acid cycle very favorable? Why and what does it help do?

A

Yes it is, due to the breaking of thioester bond in acetyl CoA. This favorability pulls the unfavorable reaction preceding it.

22
Q

Describe the second part of the beginning of the citric acid cycle:

A

The enzyme aconitase rearranges the (6C) citrate to make an intermediate cis-Aconitate that then becomes (6C) isocitrate.

23
Q

What inhibits aconitase and what has it been used for?

A

Aconitase is inbihited by fluorocitrate. Fluoroacetate is a poison (used to kill cayotes) that can be used by citrate synthase to make fluorocitrate.

24
Q

How many electrons come off total in citric acid acid? What is it more efficient than?

A

8 e- come off in pairs via 4 reduced electron carriers and GTP. It is more efficient than glycolysis.

25
Q

What is the next step after isocitrate is produced (2 things produced) ? What enzyme is used?

A

The enzyme dehydrogenase catalyzes the first decarboxylation and produces NADH and alpha ketoglutarate (5C since CO2 released).

26
Q

Why is alpha ketoglutarate an important intermediate?

A

It is involved in anaplerotic reaction related to transamination.

27
Q

What is the mechanism of the enzyme acting on alphaketo glutarate (alpha keto gluterate dehydrogenase complex) vitually identical to?

A

Identical to the mechanism in the pyruvate dehydrogenase complex and involves the same coenzymes.

28
Q

What are the products of the mechanism of alpha ketogluterate dehydrogenase complex?

A

(4C in middle) Succinyl-CoA and NADH

29
Q

What is the enzyme of the product of the only substrate level phosphorylation in the citic acid cycle after the step where Succinyl CoA is produced?

A

The enzyme succinyl-CoA synthetase used to produce GTP and (4C) succinate.

30
Q

After succinate is produced, what enzyme is used for the next step and what is the product?

A

Succinate dehydrogenase (contains a covalently linked FAD electron carrier). The products are FADH2 and fumarate.

31
Q

The reaction from succinate to fumarate using succinate dehydrogenase has what sort of energetic favorability and what is the consequence of this?

A

allows for the reaction to have a delta G0’ of zero and the reaction is reversible to produce succinate.

32
Q

After fumerate is produced, what is used and produced for the next step?

A

Water is added to fumarate (catalyzed by fumerase) to make L-malate.

33
Q

What happens after L-malate is created? Is it energetically favorable?

A

-malate dehydrogenase yields NADH and oxaloacetate. It is energeically unfavorable and is the only bump in the citric acid cycle.

34
Q

How is the bump/energetically unfavorable reaction overcome?

A

By the pulling of citrate synthase reaction that makes oxaloacetate concentrations low.

35
Q

What happens after (4C) L-malate is created?

A

It uses malate dehydrogenase to produce (4C) oxoaloacetate.

36
Q

What is the most important way that the citric acid cycle is regulated? Why?

A

The amount of NAD+ and FAD that is available. They are essential for the citric acid cycle and for the pyruvate dehydrogenase complex complex reaction?

37
Q

When all NADHs and FADH2s are converted to ATP how many ATPs are yielded per molecule of glucose? How does this compare to that yielded by glycolysis under anaerobic conditions?

A

Yields 30-38 ATP per glucose compared to the 2 from glycolysis.

38
Q

When NAD+ levels are high is the citric acid cycle favored or not?

A

It is favored. When NADH is high, it stops because NAD+ is not as abundant.

39
Q

Why is oxygen a limiting reagent in the citric acid cycle?

A

Oxygen is required for converstion of NADH to NAD+ later on.

40
Q

What is the difference between glycolysis and citric acid cycle when it comes to oxygen needs?

A

Glycolysis can use fermentation to get around needing oxygen while citric acid cycle cannot. It needs NAT+ in three of its reactions.

41
Q

What is sensitive to arsenite and mercury due to the fact that the compounds react with sulfur atoms in lipoamide of this complex? What is the treatment?

A
  • pyruvate dehydrogenase because has lipoamide in E3 of pyruvate dehydrogenase complex.
  • Can be treated with BAL which extracts arsenite from lipoamide since it also contains sulfurs that bind to arsenite.
42
Q

What are anaplerotic reactions?

Two things that are important for this in citric acid cycle?

A

Reaction involved in “filling up” of the intermediates of metabolism, which are needed for multipurposes.

-oxaloactate and alpha ketoglutarate

43
Q

Examples of anaplerotic reaction:

Example of its correction:

A
  • oxaloacetate used by making asparitc acid and must be replenished
  • Conversion of glutamic acid to alpha ketoglutarate to then convert this to oxaloacetate.
44
Q

What are citric acid cycle intermediates involved in?

A

metabolism of amino acids, fatty acids, mucleotides, and sugars.

45
Q

What are the other metabolic pathways of oxaloacetate?

A
  • converted to glucose in gluconeogenisis
  • converted to aspartate by transmination
  • converted to citrate in the citric acid cycle
46
Q

What is the Glycoxylate cycle?

What does it not do?

A
  • pathway like citric acid cycle used in plants and bacteria and produces less NADH.
  • Does not do decarboxylation
47
Q

Two additional enzymes and their roles in glyoxylate cycle:

A
  • isocitrate lyase catalyzes cleavage of isocitrate to glycoxylate and succinate
  • malate synthase catalyzes linkage of avetyl-CoA to glyoxylate to form malate
48
Q

The bypassing of decarboxylation in the glycoxylate cycle allow for what in plants and bacteria?

A

Allows them to make glucose in net amounts (more glucose) and not as much ATP.

49
Q

If plant cells need energy what will the run?

If plant cells have enough energy what will they run?

A
  • Citric acid cycle that will make more ATP and make fatty acids.
  • Glycoxylate cycle where they can make glucose instead of fatty acids (this is why plants dont get fat).

Biochem 451 Exam 1 (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions