RATE-LIMITING ENZYMES

Question 1

Rate limiting enzyme for Glycolysis

Answer 1

Enzyme : Phospofructokinase -1

( Glucose to Pyruvate )

Question 2

Rate limiting enzyme for Gluconeogenesis

Answer 2

Fructose-1,6-biphosphatase

( Glycogen to Glucose)

Question 3

Rate limiting step & enzyme for TCA Cycle?

Answer 3

Isocitrate to a-ketoglutarate using the enzyme Isocitrate dehydrogenase

Krebbs
1. Oxaloacetate
2. Citrate
3. Isocitrate
4. a-ketoglutarate - release CO2 + NADH
5. Succinyl coA - release CO2 + NADH
To
6. Succinate - release GTP
7. Fumerate - release FADH
8. Malate Back to Oxaloacetate - release FADH

Question 4

Rate limiting step and enzyme for Glycogenesis

Answer 4

From primed Glycogen + Glucose using the enzyme Glycogen synthase

Question 5

Rate limiting step and enzyme in Glycogenolysis

Answer 5

From Glycogen to Glucose 1 Phosphate using the enzyme Glycogen phosphorylase

Glycogenolysis
1. Glycogen
2. Glucose-1-phosphate
3.Glucose-6-phosphate : muscle
4. Glucose : liver

Question 6

Rate limiting step for HMP Shunt

Answer 6

G6PD

Question 7

Rate limiting step for Urea Cycle

Answer 7

Carbamoyl Phosphate Synthetase I

Question 8

Rate limiting step for Fatty Acid Synthesis

Answer 8

Acetyl coA Carboxylase

Question 9

Rate limiting step for Fatty Acid Oxidation

Answer 9

Carnitine acetyltransferase I

Question 10

Rate limiting step for ketogenesis

Answer 10

HMG-CoA Synthase

Question 11

Rate limiting step for Cholesterol synthesis

Answer 11

HMG-CoA reductase

Question 12

Rate limiting step for De novo pyrimidine synthesis

Answer 12

Carbamoyl phosphate synthetase II

Question 13

Rate limiting step for De Novo Purine Synthesis

Answer 13

Glutamine -PRPP Amidotransferase

Question 14

Pancreatic lipase is activated by ?

Answer 14

Trypsin

Question 15

Lipoprotein lipase is activated by?

Answer 15

Insulin

Question 16

Hepatic lipase action?

Answer 16

Acts on the remaining lipids carried on lipoproteins in the blood to generate LDL.

Question 17

Hormone- sensitive lipase activity is increased by?

Answer 17

Glucagon

Question 18

Responsible for the regulatory step of bile acid synthesis?

Answer 18

7-alpha-hydroxylase

Question 19

Vitamin B12 dependent enzymes? (3)

Answer 19

Methionine synthase
Methylmalonyl coA mutase
Leucine aminomutase

Question 20

Syndrome showing mutations in genes encoding peroxisome biogenesis?

Answer 20

Zellweger Syndrome

Question 21

What are the enzymes that contains copper? (4)

Answer 21

Amine oxidase
Superoxide dismutase
Cytochrome oxidase
Tyrosinase

Question 22

Rate limiting enzyme in heme synthesis?

Answer 22

ALA Synthase

Question 23

Zinc requiring enzymes in Heme synthesis? (2)

Answer 23

1. ALA dejydratase
2. Ferochelatase

Question 24

Steps that undergoes spontaneous oxidation ( no enzyme needed) in heme synthesis? (3)

Answer 24

1. uroporphyrinogen III —-> coproporphyrinogen III
2. coproporphyrinogen III ——> protophhrinogen IX
3. protophyrinogen IX ——> protoporphyrin IX

Question 25

Enzymes acting as free radical scavenging systems? (3)

Answer 25

1. Catalase , present in peroxisomes, decomposes H2O2 to O2 and 2 mol H20.
2. Superoxide dismutase (SODs)- convert O2 to H2O2.
3. Glutathione peroxidase- catalyzes free radical breakdown from H2O2 or 2OH + 2GSH into GSSG + 2 mol H2O