lecture 13 TCA

Question 1

purpose of citric acid cycle?

Answer 1

harvest high-energy electrons (captured in the form of NADH and FADH2) from acetyl CoA as it is oxidized to CO2

Question 2

what’s the point of capturing energy in the form of NADH and FADH2 from TCA cycle?

Answer 2

These reduced molecules will create the proton gradient that powers ATP synthesis

Question 3

The key control points in the citric acid cycle are the reactions catalyzed by :

Answer 3

isocitrate dehydrogenase and α-ketoglutarate dehydrogenase.

Question 4

____controls entry of glucose-derived acetyl CoA into the cycle.

Answer 4

pyruvate dehydrogenase

Question 5

name the locations where the 3 NADH’s are generated in the citric acid cycle

Answer 5

isocitrate -> a-KTG, a-KTG->succinyl coA, malate -> oxaloacetate

Question 6

___ is both a final product and a starting substrate

Answer 6

Oxaloacetate

Question 7

overall reaction TCA cycle

Answer 7

3 NAD+ + FAD+ acetyl co-A + ADP + P —> 3 NADH + FADH2 + ATP + coA

Question 8

name the 3 transamination reactions

Answer 8

1. Transamination reactions convert alanine into pyruvate as α-ketoglutarate is converted into glutamate. Aspartate becomes oxaloacetate in the same manner.
2. Glutamate can be deaminated directly to form α-ketoglutarate.

Question 9

which steps create CO2?

Answer 9

isocitrate to a-KTG and aKTG to succinyl coA

Question 10

what’s the point of CO2 here?

Answer 10

waste product- gets expelled

Question 11

a-KTG + coA = ?

Answer 11

succinyl coA

Question 12

the enzyme for this reaction adds a high energy thioester bond to coA, releasing CO2 in the process and converting NAD+ to NADH

Answer 12

a-KTG to succinyl coA

Question 13

like NADH, ___ is an energy carrier that carries electrons to the electron transport chain

Answer 13

FADH2

Question 14

which step involves substrate level phosphorylation

Answer 14

succinyl co A to succinate. why? because we’re ripping off that high energy thiol bond

Question 15

what is formed from the oxidative decarboxylation of a-KTG?

Answer 15

succinyl coA

Question 16

a-ketoglutarate dehydrogenase complex

Answer 16

three kinds of enzymes that is structurally similar to

the pyruvate dehydrogenase complex.

Question 17

explain what happens when succinyl coA becomes succinate

Answer 17

energy inherent in the thioester molecule is transformed into phosphoryl-group-transfer potential, an example of substrate-level phosphorylation

Question 18

what’s the big difference between citrate and isocitrate?

Answer 18

The isomerization of citrate to isocitrate moves a hydroxyl group with a hydrogen group, bringing it closer to the COO-

Question 19

what are the 2 control points in the TCA?

Answer 19

isocitrate dehydrogenase and a-ketoglutarate dehydrogenase.

Question 20

Isocitrate dehydrogenase is allosterically

stimulated by :

Answer 20

ADP, which signifies the need for more energy.

Question 21

a-ketoglutarate dehydrogenase

is inhibited by high levels of :

Answer 21

ATP. Thus, the rate of the cycle is decreased when the

cell has high levels of ATP and NADH.

Question 22

where specifically does TCA cycle occur

Answer 22

mito matrix