10.4-10.5 Regulation of Citrate Cycle

Question 1

What enzymes correspond with CC regulation?

Answer 1

Pyruvate dehydrogenase, citrate synthase, isocitrate dehydrogenase, a-ketoglutarate dehydrogenase, pyruvate carboxylase

Question 2

Pyruvate dehydrogenase regulation governed by…?

Answer 2

Regulation governed by energy charge

Question 3

What happens to inhibit pyruvate dehydrogenase?

Answer 3

Kinase phosphorylates Ser on E1

Question 4

What happens to activate pyruvate dehydrogenase?

Answer 4

phosphatase removes that phosphate on Ser on E1

Question 5

Why does calcium inactivate pyruvate dehydrogenase kinase?

Answer 5

Leads to muscle contraction
Let dehydrogenase work to continue the citric acid cycle

Question 6

What enzyme regulates E1 of pyruvate dehydrogenase?

Answer 6

Pyruvate dehydrogenase kinase

Question 7

What are the activators of pyruvate dehydrogenase kinase?

Answer 7

ATP, Acetyl CoA, NADH

Question 8

What are the inhibitors of pyruvate dehydrogenase kinase?

Answer 8

NAD+, CoA, ADP, Calcium

Question 9

What activates pyruvate dehydrogenase phosphatase 1?

Answer 9

Calcium

Question 10

What are the irreversible reactions of CC?

Answer 10

1, 3, 4

Question 11

What kind of things regulate the CC?

Answer 11

substrate availability, energy charge, feedback inhibition, NADH/NAD+ ratio, calcium concentration, succinyl-coA (GTP production)

Question 12

What activates pyruvate dehydrogenase?

Answer 12

NAD+, CoA, ADP, Calcium (reactants)

Question 13

What inhibits pyruvate dehydrogenase?

Answer 13

NADH, acetyl coa, ATP (products)

Question 14

What activates citrate synthase?

Answer 14

ADP

Question 15

What inhibits citrate synthase?

Answer 15

NADH, citrate, ATP, succinyl-coa

Question 16

What are the activators and inhibitors of isocitrate dehydrogenase?

Answer 16

Activators - ADP and calcium
Inhibitors - NADH and ATP

Question 17

What activates and inhibits a-ketoglutarate dehydrogenase?

Answer 17

Activates - AMP, calcium
Inhibits- NADH, succinyl-CoA, ATP

Question 18

What is Citric acid used for?

Answer 18

commercial food preservative, isolated from lemons

Question 19

How do you Maximize citrate production?

Answer 19

Experimental setup
Culture conditions inhibit:
* Reactions 2-8
* Citrate lyase
Mold strain with high capacity for citrate export out of the mitochondria and then inhibited reformation of acetyl CoA

Question 20

What is the Importance of citrate cycle? (3)

Answer 20

-Citrate cycle generates redox power by oxidizing acetyl -CoA– Reduces NAD+ & FAD
-Provides precursors for many other pathways
-Intermediates are shared by other pathways

Question 21

Name two useful intermediates of the CC?

Answer 21

a-ketoglutarate and citrate

Question 22

What is a-ketoglutarate used for?

Answer 22

glutamate synthesis
Reductive amination reaction
Reducing power comes from NADH
Glu is precursor for other AAs

Question 23

What is citrate important for?

Answer 23

Exported to cytosol
* Citrate lyase
* Used to make acetyl-CoA:
– Precursor for fatty acid and cholesterol synthesis

Question 24

How is acetyl coA transported?

Answer 24

Via citrate; citrate lysis to free acetyl CoA (citrate shuttle)

Question 25

What kind of pathway is the CC?

Answer 25

amphibolic pathway
– Functions as both a catabolic and anabolic pathway
– Reactions replenish CC intermediates

Question 26

What two substrates of the CC can leave the mitochondria?

Answer 26

pyruvate and citrate

Question 27

What do high-energy molecules do?

Answer 27

Inhibit the citric acid cycle