Hexose Monophosphate Shunt

Question 1

What is the HMP Shunt?

Answer 1

Metabolic pathway parallel to glycolysis, producing NADPH and intermediates for nucleic acid and amino acid synthesis.

Question 2

Where does the HMP Shunt occur in animals and plants?

Answer 2

Cytoplasm (animals) and plastids (plants).

Question 3

What are the main functions of the HMP Shunt?

Answer 3

• Produces NADPH for reductive biosynthesis and antioxidant defense
• Supplies ribose-5-phosphate for nucleotide synthesis
• Provides intermediates like erythrose-4-phosphate for amino acid biosynthesis

Question 4

What is the irreversible phase of the HMP Shunt called?

Answer 4

Oxidative Phase

Question 5

List the key steps of the Oxidative Phase.

Answer 5

• Glucose-6-phosphate → 6-phosphoglucono-lactone (via Glucose-6-phosphate dehydrogenase)
• 6-phosphoglucono-δ-lactone → 6-phosphogluconate (via 6-phosphogluconolactonase)
• 6-phosphogluconate → Ribulose-5-phosphate (via 6-phosphogluconate dehydrogenase)

Question 6

What are the products of the Oxidative Phase?

Answer 6

• NADPH
• Ribulose-5-phosphate

Question 7

What is the reversible phase of the HMP Shunt called?

Answer 7

Non-Oxidative Phase

Question 8

List the key steps of the Non-Oxidative Phase.

Answer 8

• Ribulose-5-phosphate → Ribose-5-phosphate (via ribose-5-phosphate isomerase)
• Xylulose-5-phosphate + Ribose-5-phosphate → Glyceraldehyde-3-phosphate + Sedoheptulose-7-phosphate (via transketolase)
• Sedoheptulose-7-phosphate + Glyceraldehyde-3-phosphate → Fructose-6-phosphate + Erythrose-4-phosphate (via transaldolase)

Question 9

What enzymes are key to the HMP Shunt?

Answer 9

• Glucose-6-phosphate dehydrogenase
• Transketolase
• Transaldolase

Question 10

What is the clinical significance of Glucose-6-Phosphate Dehydrogenase Deficiency?

Answer 10

Impairs NADPH production, leading to oxidative damage in red blood cells (linked to malaria resistance).

Question 11

How is Thiamine Deficiency related to the HMP Shunt?

Answer 11

Transketolase activity is used as a diagnostic marker.

Question 12

Fill in the blank: Glucose-6-phosphate can proceed through glycolysis or enter the _______ based on cellular needs.

Answer 12

HMP shunt

Question 13

Why is the HMP pathway called a ‘shunt’?

Answer 13

It diverts glucose-6-phosphate from glycolysis for NADPH and ribose-5-phosphate production.

Question 14

What is the main function of the HMP Shunt?

Answer 14

Producing NADPH for biosynthesis and ribose-5-phosphate for nucleotides.

Question 15

What is NADPH essential for?

Answer 15

• Fatty acid synthesis
• Cholesterol synthesis
• Defense against oxidative stress

Question 16

What is Ribose-5-phosphate a precursor for?

Answer 16

Nucleotides and nucleic acids.

Question 17

What intermediates are produced in the HMP Shunt?

Answer 17

• Glyceraldehyde-3-phosphate
• Fructose-6-phosphate
• Erythrose-4-phosphate