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Flashcards in CAC Deck (18)
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1
Q

Where does the citric acid cycle occur?

A

The mitochondrial matrix

2
Q

How does the cycle use electrons?

A

It removes electrons and passes them on to form NADH and FADH2.

3
Q

How is the CAC very efficient?

A

It is cyclical, small number of citric acid cycle molecules can make loads of NADH and FADH2.

4
Q

What % of aerobic cell energy does the CAC in collaboration with oxidative phosphorylation produce?

A

90%

5
Q

How much ATP is produced through fermentation?

A

2 mol ATP per Glc molecule

6
Q

How did the citric acid cycle evolve?

A

The CAC evolved to harvest electrons that could then be used to completely oxidise food molecules to CO2 and H2O.

7
Q

Acetyl CoA in the cycle

A

Pyruvate from glycolysis and fatty acids are oxidised further to acetyl CoA in the mitochondrial matrix.

8
Q

How is Acetyl CoA made?

A

Made from pyruvate, through the action of the enzyme pyruvate dehydrogenase. Very complicated series of reactions involving decarboxylation of the pyruvate molecule,then oxidation,followed by the transfer of the CoA complex.

9
Q

How many electrons are produced during the decarboxylation step?

A

The decarboxylation step releases two electrons (in the form of 2 H ions), which can pass to O2 to produce more ATP through NADH intermediates.

10
Q

Pyruvate dehydrogenase

A

It contains tens of copies of each enzyme sub-unit (E1, E2, E3). Each sub-unit catalyses a different part of the reaction to convert pyruvate to acetyl CoA.

11
Q

Pyruvate dehydrogenase - action of E1

A

E1 catalysis the first decarboxylation of pyruvate.

12
Q

Pyruvate dehydrogenase - action of E2

A

E2 transfers the acetyl group to coenzyme A.

13
Q

Pyruvate dehydrogenase - action of E3

A

E3 recycles the lipoyllysine through the reduction of FAS, which is recycled by passing electrons to NAD+.

14
Q

Acetyl CoA in the citric acid cycle

A

Acetyl CoA (C2) enters the “black box” of the citric acid cycle. Each turn, 2C’s enter (acetyl CoA) followed by removal of two different C’s as 2x CO2.

15
Q

How is pyruvate dehydrogenase regulated?

A

It is regulated by it’s immediate products and the end point of cellular respiration, ATP.
It’s regulated depending on the needs of the cell.

16
Q

2 other points of control in CAC

A

1st one - isocitrate dehydrogenase
2nd one - a-ketoglutarate dehydrogenase
Both points are at non-reversible reactions (exergonic steps).
These control points allow re-direction of cellular resources.

17
Q

What is an anaplerotic reaction?

A

A reaction that replenishes the concentration of an intermediate in a metabolic pathway

18
Q

How can pyruvate be converted to oxaloacetate?

A

Pyruvate can be converted to oxaloacetate by the enzyme pyruvate carboxylase.
Pyruvate carboxylase is only active when acetyl CoA is present, so a build up of acetyl CoA triggers this reaction.