MMT: TCA cycle

Question 1

Which TCA cycle intermediate(s) can be used for fatty acid synthesis?

Answer 1

citrate

Question 2

Which TCA intermediate(s) can be used for amino acid synthesis

Answer 2

a-ketogluterate and oxaloacetate

Question 3

Which TCA cycle intermediate(s) can be used in heme synthesis

Answer 3

Succinyl CoA

Question 4

Which TCA cycle intermediate(s) can be used in gluconeogenesis?

Answer 4

malate and oxaloacetate

Question 5

Can TCA cycle operate when there is no oxygen? Can glycolysis?

Answer 5

no; yes

Question 6

where are the enzymes for the TCA cycle found?

Answer 6

the mitochondrial matrix

Question 7

What do we do with pyruvate in anaerobic conditions?

Answer 7

Lactate fermentation; we convert pyruvate to lactate and 2 protons, generating NAD+ in the process

Question 8

How does pyruvate enter the matrix?

Answer 8

It enters the intermembrane space through a VDAC pore, then enters the matrix via an MPC. The negative charge on pyruvate must be balanced, so a proton enters with the pyruvate.

Question 9

list the intermediates in the TCA cycle

Answer 9

citrate, isocitrate, a-ketogluterate, succinyl CoA, succinate, fumrate, malae, oxaloacetate

Question 10

list the enzymes in the TCA cycle

Answer 10

aconitase, isocitrate dehydrogenase, a-ketogluterate dehydrogenase, sunnincyl CoA synthase, succinate dehydrogenase, fumrase, malate dehydrogenase, citrate synthase

Question 11

List the enzymes that yield CO2

Answer 11

Isocitrate dehydrogenase, a-ketoglutarate dehydrogenase

Question 12

List the enzymes that yield NADH

Answer 12

Isocitrate dehydrogenase, a-ketoglutarate dehydrogenase, malate dehydrogenase

Question 13

List the enzymes that yield GTP

Answer 13

Succinyl CoA synthase

Question 14

List the enzymes that yield FADH2

Answer 14

succinate dehydrogenase

Question 15

What high energy bond is found in acetyl CoA

Answer 15

thioester bond

Question 16

What is the rate-limiting reaction in the TCA cycle?

Answer 16

Isocitrate dehydrogenase

Question 17

Note the biological roles of GTP.

Answer 17

Protein synthesis, signal transduction, or convert to ATP

Question 18

18. Calculate the yield of ATP from the oxidation of acetyl CoA.

Answer 18

10; 2.5 per NADH, 1.5 per FADH2, and 1 GTP

Question 19

What is the role of the pyruvate dehydrogenase component of pyruvate dehydrogenase complex? What prosthetic group does it need?

Answer 19

Oxidative decarboxylation of pyruvate; TPP

Question 20

What is the role of the dihidrolipoyl transacetylase in the pyruvate dehydrogenase complex? What prosthetic group does it require?

Answer 20

Transfers an acetyl group to CoA; lipoamide

Question 21

What is the role of the dihidrolipoyl dehydrogenase in the pyruvate dehydrogenase complex? What prosthetic group does it require?

Answer 21

Regenerates the oxidized form of lipoamide; FAD

Question 22

Lipoamide is connected to what amino acid? What is the important bond in the complex?

Answer 22

Lysine; a reactive disulfide bond

Question 23

describe the the two general ways pyruvate dehydrogenase can be regulated?

Answer 23

energy charge: high ATP/NADH deactivates pyruvate dehydrogenase

phosphorylation: phosphorylating pyruvate dehydrogenase deactivates it

Question 24

dephosphorylating pyruvate dehydrogenase is influenced by which two molecules?

Answer 24

calcium and insulin; both increase pyruvate dehydrogenase

Question 25

leigh’s disease: what causes it, whata re the symptoms, and where are the mutations found

Answer 25

Direct mutation in pyruvate dehydrogenase. Impaired mitochondrial function, chronic lack of energy and CNS issues. We’ll convert pyruvate to lactate and develop metabolic acidosis. Mutation can be in E1 component or PDH phosphatase

Question 26

how can leigh’s disease be treated

Answer 26

Can be treated with thiamine, taking in leucine and lysine, high fat and low carb diet, oral bicarb or citrate

Question 27

Arsenic impacts what enzyme in the pyruvate dehydrogenase complex

Answer 27

E2 of the Pyruvate dehydrogenase complex; it binds to lipoic acid causing an accumulation of lactate that will impact the brain and lead to death

Question 28

What conditions can be associated with altered PDH levels?

Answer 28

Alzheimer’s and Parkinson’s, leigh’s disease, type II diabetes

Question 29

Low iron would impact which enzyme in the TCA cycle?

Answer 29

aconitase

Question 30

Compare the reactions catalyzed by the α-ketoglutarate dehydrogenase complex to those catalyzed by the pyruvate dehydrogenase complex.

Answer 30

They require the same cofactors but have slightly different enzymes. They are both made of an E1, E2, and E3, with just minor changes.

Question 31

Describe the role of anaplerotic reactions and specifically the function of pyruvate carboxylase to replenish oxaloacetate

Answer 31

Used to make more oxaloacetate so we can make more energy via gluconeogenesis or amino acid synthesis without stalling the TCA cycle

Question 32

Oxaloacetate can be used to make ___

Answer 32

Glucose via gluconeogenesis