Rate limiting Steps

Question 1

Bile Acid Synthesis

Answer 1

7a-hydroxylase

Question 2

Cholesterol Synthesis

Answer 2

HMG-CoA reductase

HMG-CoA to mevalonate

Question 3

Urea Cycle

Answer 3

Carbomoyl phosphate synthetase I

Question 4

HMP shunt (pentose Phosphate pathway)

Answer 4

Glucose 6-phosphate Dehydrogenase

Activation: NADP+
Inhibition: NADH

Question 5

Glycolysis

Answer 5

PFK-1

Activation: AMP, fructose 2,6 bisphosphate
Inhibition: ATP, citrate

Question 6

Gluconeogenesis

Answer 6

Fructose 1,6 Bisphosphatase

Activation: ATP, acetyl CoA
Inhibition: AMP, fructose 2,6 bisphosphate

Question 7

TCA cycle

Answer 7

Isocitrate dehydrogenase

Activation: ADP
Inhibition: ATP, NADH

Question 8

Glycogenesis

Answer 8

Glycogen synthase

Activation: glucose 6 phosphate, Insulin, cortisol
Inhibition: epinephrine, glucagon

Question 9

Glycogenolysis

Answer 9

Glycogene phosphorylase

Activation: epinephrine, glucagon, AMP
Inhibition: glucose 6 phosphate, insulin, ATP

Question 10

De novo pyrimidine synthesis

Answer 10

Carbomoyl phosphate syntehtase II

Question 11

De novo purine synthesis

Answer 11

Glutamine-phosphoribosylpyrophosphate (PRPP) amidotransferase

Inhibition: AMP, IMP, GMP

Question 12

Urea Cycle

Answer 12

Carbomoyl phosphate synthetase I

Activation: N-acetylglutamate

Question 13

Fatty Acid Synthesis

Answer 13

Acetyl CoA carboxylase

Activation: insulin, citrate
Inhibition: glucagon, palmitoyl-CoA

Question 14

Fatty acid oxidation

Answer 14

Carnitine acyltransferase I

Inhibited by malonyl CoA

Question 15

Ketogenesis

Answer 15

HMG-CoA synthase

Question 16

Cholesterol synthesis

Answer 16

HMG CoA reductase

Activated by insulin, thyroxine
Inhibited by glucagon, cholesterol