KREBS

Question 1

What are the 3 points of regulation in Krebs?

Answer 1

1. Pyruvate Dehydrogenase (PDH)
2. Isocitrate dehydrogenase
3. OAA

Question 2

What is responsible for inhibiting PDH activity

Answer 2

1. high [acetyl CoA}
2. high [NADH}
3. high [ATP]
4. low [pyruvate]

Question 3

Where does KREBS occur?

Answer 3

Mitochondria

Question 4

At what point is KREBS irreversible

Answer 4

When alpha-ketoglutarate is formed

Question 5

KREBS can only occur when what is present?

Answer 5

Oxygen

Question 6

What is the main goal of the TCA Cycle?

Answer 6

Generate x3 NADH and x1 FADH2

Question 7

Why are the products of NADH and FADH2 such important outcomes of the TCA cycle?

Answer 7

The generation of these molecules can subsequently leave the TCA cycle and go onto the electron transport chain, which generates the highest yield of ATP.

Question 8

To start the TCA cycle, Acetyle CoA turns into what?

Answer 8

Citrate

Question 9

In the TCA cycle (2nd step) Citrate is converted into what?

Answer 9

Isocitrate

Question 10

In the TCA cycle (3rd step) Isocitrate is converted into what & what is the yield from this conversion?

Answer 10

Alpha-Ketoglutarate (yields 1 NADH molecule)

Question 11

In the TCA cycle (4th step) Alph-Ketoglutarate is converted into what & what is the yield from this conversion?

Answer 11

Succinyl-CoA (yields 1 NADH molecule)

Question 12

Succinyle-CoA sheds ____ to become what?

Answer 12

Sheds CoA (TCA cycle produces x1 CoA molecule from this step), to become Succinate

Question 13

In the TCA cycle (6th step) Succinate is converted into what & what is the yield from this conversion?

Answer 13

Fumarate (yields 1 FADH2 molecule)

Question 14

In the TCA cycle (7th step) Fumarate is converted into what?

Answer 14

Malate

Question 15

In the TCA cycle (8th step) Malate is converted into what & what is the yield from this conversion?

Answer 15

Oxaloacetate (yields 3rd & final NADH molecule)

Question 16

What is the rate-limiting enzyme of the TCA cycle and what step does it occur at?

Answer 16

Isocitrate Dehydrogenase (occurs when converting Isocitrate to Alpha-Keoglutarate)

Question 17

In the presence of ADP, what will the body do with regard to the TCA cycle & why?

Answer 17

It will stimulate the TCA cycle to produce NADH / FADH2 to be used in the ETC to produce the ATP that the body needs.

Question 18

In the presence of ATP, what will the body do with regard to the TCA cycle & why?

Answer 18

There is no need to stimulate the TCA cycle b/c the body already has usable ATP.

Question 19

What is the enzyme that catalyzes Acetyle CoA into Citrate?

Answer 19

Citrate Synthase

Question 20

What is the enzyme that catalyzes Citrate into Isocitrate?

Answer 20

Aconitase

Question 21

What is the enzyme that catalyzes Alph-Ketoglutarate into Succinyl-CoA?

Answer 21

Alpha-Ketoglutarate Dehydrogenase

Question 22

What is the enzyme that catalyzes Succinyl-CoA into Succinate?

Answer 22

Succinate Thiokinase

Question 23

What is the enzyme that catalyzes Succinate into Fumarate?

Answer 23

Succinate Dehydrogenase

Question 24

What is the enzyme that catalyzes Fumarate into Malate?

Answer 24

Fumarase

Question 25

What is the enzyme that catalyzes Malate into Oxaloacetate?

Answer 25

Malate Dehydrogenase

Question 26

What is the common theme of all the enzymes that produce critical molecules of the TCA cycle (NADH / FADH2)?

Answer 26

Dehydrogenase = NADH or FADH2 yield

Question 27

For all the steps of the TCA cycle that produce NADH, what is a way to remember molecules produce it as byproduct of catalyzing with an enzyme?

Answer 27

I(Isocitrate), K(Ketoglutarate), M(Malate)

NADH = MIDDLE of the alphabet

Question 28

For the step in the TCA cycle that produces FADH2, what is a way to remember which molecule produce it as byproduct?

Answer 28

F(Fumarate) = F(FADH2)

Same letter of the alphabet