Carbohydrates Metabolism

Question 1

What is the rate limiting step in Glycolysis?

Name the activators and inhibitors of it.

Answer 1

PFK-1. Activated by AMP, F2,6,BP (dephosphorylated state)

Inhibited by: ATP, citrate (phosphorylated state)

Question 2

Which enzyme produces the only NADH in the Glycolysis pathway? what are the substrates involved?

Answer 2

Glyceraldehyde 3-P Dehydrogenase. Converts G3P to 1,3 BPG.

Question 3

Enzyme responsible for Last irreversible step in Glycolysis

Specify regulations of this enzyme.

Answer 3

Pyruvate Kinase.
Activated by F1,6,BP and Insulin. Active in the dephosphorylated form.
Inhibited by Glucagon, ATP, Alanine. Inactive in the phosphorylated form.

Question 4

What causes Tarui Disease?

Answer 4

Deficiency in PFK1: Hemolytic anemia

Question 5

Where does Gluconeogenesis occur?

Answer 5

Liver, kidney, small intestine

Question 6

What is the first step enzyme in Gluconeogenesis? Where is it located? Activators and inhibitors?

Answer 6

Pyruvate Carboxylase: located in mitochondria.
Converts Pyruvate to Oxaloacetate.
Activated by: Acetyl CoA and cortisol.

Question 7

Rate limiting step of Gluconeogenesis. Activators and Inhibitors

Answer 7

Fructose 1,6 Biphosphotase. Activated by Cortisol and Citrate. Inhibited by AMP and F2,6BP.

Question 8

What is Fructose 1,6-biphosphotase deficiency?

Answer 8

Gluconeogenesis disorder: similar to Tarui disease. Hypoglycemia.

Question 9

Von Gierke disease

Answer 9

Deficiency in the G-6 Phosphatase of Gluconeogenesis.: hypoglycemia, lactic acidosis.

Question 10

Fanconi-Bickel Syndrome

Answer 10

mutation in GLUT 2 transporter.

Question 11

Pathway of Glucose to Fructose

Answer 11

Glucose-Sorbitol-Fructose

Enzymes: Aldose reductase, Sorbitol dehydrogenase.

Question 12

What causes Sorbitol accumulation

Answer 12

Deficiency in the enzyme Sorbitol Dehydrogenase which converts Sorbitol to Fructose.

Question 13

Rate limiting enzyme of Galactose metabolism

Answer 13

GALT

Question 14

What causes Galactosemia?

Answer 14

Deficiency in GALT: leads to accumulation of Galactic

Deficiency in Galactokinase: leads to accumulation of galactose and galacticol in blood and urine.

Question 15

Rate limiting step of PPP and it’s function

Answer 15

G6P Dehydrogenase: reduces NADP to NADPH and oxidizes G6P to 6-phosphoglucono-lactone. Part of the “Oxidative” phase. Inhibited by NAPDH

Question 16

Which cells have the highest PPP activity?

Answer 16

phagocytic cells

Question 17

What is the Rate Limiting Enzyme in Glycogenesis and the substrates involved?
In which form is it active?

Answer 17

Glycogen Synthase. Converts UDP-Glucose to Glycogen.

It is active in the dephosphorylated form.

Question 18

What is the branching enzyme used in Glycogenesis

Answer 18

glucose 4:6 transferase

Question 19

What is the Rate limiting enzyme of Glycogenolysis?
What co-factor does it use?
In which state is it active?

Answer 19

Glycogen Phosphorylase. Uses B6 as co-factor.

Active in the phosphorylated form.