10.4-10.5 Regulation of the citrate cycle

Question 1

how is pyruvate dehydrogenase regulated? (generally)

Answer 1

by energy charge

Question 2

how is pyruvate dehydrogenase inhibited?

Answer 2

when energy charge is high, pyruvate dehydrogenase kinase phosphorylates serine on E1

Question 3

how is pyruvate dehydrogenase activated?

Answer 3

when energy charge is low, phosphatase removes that phosphate from serine on E1

Question 4

what 3 molecules inhibit pyruvate dehydrogenase?

Answer 4

1. NADH
2. acetyl-CoA
3. ATP

Question 5

what 4 molecules activate pyruvate dehydrogenase?

Answer 5

1. NAD+
2. CoA
3. ADP
4. also Ca2+

Question 6

what 3 reactions are irreversible in the citrate cycle?

Answer 6

1, 3, 4

Question 7

describe the general porcess of citrate cycle inhibition

Answer 7

products generally inhibit the enzymes that created them by feedback inhibition

Question 8

describe the general process of citrate cycle activation

Answer 8

activators are generally on the reactant side, driving the reactions forward

Question 9

how is citrate synthase activated (1)? inhibited (4)?

Answer 9

activated: by ADP
inhibited: NADH, citrate, ATP, succinyl-CoA

Question 10

how is isocitrate dehydrogenase activated (2)? inhibited? (2)

Answer 10

activated: ADP and Ca2+
inhibited: NADH, ATP

Question 11

how is alpha-ketogluterate dehydrogenase activated (2)? inhibited (3)?

Answer 11

activated: AMP, Ca2+
inhibited: NADH, succinyl-CoA, ATP

Question 12

how is pyruvate decarboxylase activated?

Answer 12

Acetyl-CoA

Question 13

how is citric acid uses commercially? where is it obtained from?

Answer 13

used as a commercial food preservative, obtained from lemons

Question 14

how was citrate production maximized experimentally?

Answer 14

used culture conditions that inhibit citrate lyase and reactions 2-8 of the citrate cycle, yielding a mold strain with a high capacity for citrate export

Question 15

how does the citrate cycle generate redox energy? what does this redox energy do?

Answer 15

generates redox energy by oxidizing acetyl-CoA which reduces NAD+ and FAD

Question 16

other than energy and energy molecules, what does the citrate cycle provide?

Answer 16

precursors for many other pathways as intermediates are shared by other pathways

Question 17

what is alpha-ketogluterate also used for? how?

Answer 17

glutamate synthesis via a reductive amination reaction whose reducing power comes from NADH

Question 18

what is glutamate a precursor for?

Answer 18

many other amino acids