TCA Cycle

Question 1

What is citrate from the TCA cycle used for?

Answer 1

fatty acid and sterol synthesis

Question 2

what is alpha ketogluterate from the TCA cycle used for?

Answer 2

amino acid synthesis (neurotransmitters)

Question 3

what is succinyl CoA from the TCA cycle used for?

Answer 3

heme synthesis

Question 4

what is malate from the TCA cycle used for?

Answer 4

gluconeogenesis

Question 5

what is oxaloacetate from the TCA cycle used for?

Answer 5

amino acid synthesis

Question 6

what happens to the TCA cycle when intermediates are removed?

Answer 6

slows down because there is no oxaloacetate

Question 7

What is an anapleurotic reaction?

Answer 7

reaction that returns intermediates to the TCA cycle

Question 8

what is the most important anapleurotic reaction?

Answer 8

pyruvate carboxylase- conversion of pyruvate to oxaloacetate when Acetyl-CoA accumulates (means there is no oxaloacetate to react with Acetyl-CoA–> triggers conversion of pyruvate to oxaloacetate)

Question 9

what is the role of pyruvate dehydroxylase?

Answer 9

convert pyruvate to oxaloacetate when acetyl-CoA builds up

Question 10

where is pyruvate carboxylase activity highest?

Answer 10

liver and neuron mitochondria

Question 11

what are the steps of pyruvate carboxylase reaction?

Answer 11

ATP + HCO₃^- + pyruvate (pyruvate carboxylase)–> oxaloacetate

pyruvate has 3 carbons, oxaloacetate has 4

extra carbon comes from HCO₃^-

Question 12

what is the key regulated step of the TCA cylce?

Answer 12

isocitrate dehydrogenase

Question 13

how is the isocitrate dehydrogenase reaction regulated?

Answer 13

activated by ADPregulated by ATP/ADP ratio

inhibited by ATP

Question 14

what happens when the TCA cycle is inhibited at the key regulatory step?

Answer 14

citrate leaves the TCA cycle for other uses

Question 15

what does loss of citrate require for the TCA cycle to continue?

Answer 15

anapleurotic reaction to replenish citrate to replenish oxaloacetate (pyruvate carboxylase reaction)