Biochemistry rate-limiting enzymes

Question 1

For each process, state the rate limiting enzyme, and molecules that either inhibit or promote the process (regulators)

Answer 1

Don’t memorize, but think where each step fits into the grand scheme.

Question 2

Glycolysis

Answer 2

Phosphofructokinase-1 (PFK-1)

+ AMP, Fructose 2,6BP
-ATP, citrate

Question 3

Gluconeogenesis

Answer 3

FBP-1 (Fructose 1,6 Bisphosphatase)

+ ATP, Acetyl CoA
- AMP, fructose 2,6 bisphosphate

Question 4

TCA cycle

Answer 4

Isocitrate dehydrogenase

+ ADP
- NADH, ATP

Question 5

Glycogenesis

Answer 5

Glycogen synthase

+ G6P, insulin, cortisol
- epinephrine, glucagon

Question 6

Glycogenolysis

Answer 6

Glycogen phosphorylase

+ epinephrine, glucagon, AMP
- G6P, insulin, ATP

Question 7

HMP shunt

Answer 7

Glucose 6 phosphate dehydrogenase

+ NADP+
- NADPH

Question 8

Fatty acid synthesis

Answer 8

Acetyl CoA Carboxylase (ACC)

+ Insulin, citrate
- Glucagon, palmytoyl CoA

Question 9

Fatty acid oxidation (negative regulator only)

Answer 9

Carnitine acyltransferase I

• Malonyl CoA

Question 10

Ketogenesis (enzyme only)

Answer 10

HMG-CoA synthase

Question 11

Cholesterol synthesis

Answer 11

HMG-CoA reductase

+ Insulin, thyroxine
- Glucagon, cholesterol