HMP Shunt, NADPH & Simple Sugar 2025

Which molecule inhibits glucose-6-phosphate dehydrogenase?

• A. NADP⁺

• B. NADPH

• C. Glutathione

• D. Ribulose-5-phosphate

Answer: B. NADPH

Which enzyme produces ribulose-5-phosphate?

• A. G6PD

• B. Transaldolase

• C. 6-Phosphogluconate dehydrogenase

• D. Transketolase

Answer: C. 6-Phosphogluconate dehydrogenase

What is the primary function of transketolase?

• A. Produces NADPH

• B. Transfers 2-carbon units

• C. Oxidizes glutathione

• D. Generates ribose-5-phosphate

Answer: B. Transfers 2-carbon units

Which pathway is the primary source of NADPH in erythrocytes?

• A. Glycolysis

• B. TCA cycle

• C. Pentose phosphate pathway

• D. Fatty acid oxidation

Answer: C. Pentose phosphate pathway

What is the role of glutathione peroxidase?

• A. Reduces H₂O₂ to water

• B. Produces NADPH

• C. Transfers electrons to cytochrome P450

• D. Synthesizes nitric oxide

Answer: A. Reduces H₂O₂ to water

Which enzyme is responsible for transferring 3-carbon units in the non-oxidative phase of the PPP?

• A. Transketolase

• B. Transaldolase

• C. 6-Phosphogluconate dehydrogenase

• D. G6PD

Answer: B. Transaldolase

What is the primary role of NADPH in erythrocytes?

• A. Generate ATP

• B. Maintain reduced glutathione

• C. Produce ribose-5-phosphate

• D. Facilitate glycolysis

Answer: B. Maintain reduced glutathione

Which phase of the PPP directly links to glycolysis?

• A. Oxidative phase

• B. Non-oxidative phase

• C. Both phases

• D. Neither phase

Answer: B. Non-oxidative phase

Which molecule is essential for the activity of glutathione reductase?

• A. FAD

• B. NADPH

• C. GTP

• D. CoA

Answer: B. NADPH

What is the primary precursor for the PPP?

• A. Ribulose-5-phosphate

• B. Fructose-6-phosphate

• C. Glucose-6-phosphate

• D. Glyceraldehyde-3-phosphate

Answer: C. Glucose-6-phosphate

NADPH is produced in the oxidative phase of the PPP.

Answer: True
Explanation: NADPH is generated during the dehydrogenation of glucose-6-phosphate and oxidative decarboxylation of 6-phosphogluconate.

Ribose-5-phosphate is only produced in the oxidative phase of PPP.

Answer: False
Explanation: Ribose-5-phosphate can also be formed in the non-oxidative phase via sugar interconversions.

Erythrocytes depend solely on the PPP for NADPH production.

Answer: True
Explanation: Erythrocytes lack other pathways for NADPH generation.

Transketolase requires biotin as a coenzyme.

Answer: False
Explanation: Transketolase requires thiamine pyrophosphate (TPP) as a coenzyme.

Reactive oxygen species can cause oxidative stress.

1. Answer: True
   Explanation: ROS like H₂O₂ damage cellular components, leading to cell death and inflammation.

The Pentose Phosphate Pathway produces ATP.

Answer: False
Explanation: The PPP does not directly produce or consume ATP; its primary outputs are NADPH and ribose-5-phosphate.

NADPH is required for fatty acid and cholesterol synthesis.

• Answer: True
  Explanation: NADPH provides reducing equivalents necessary for biosynthetic reactions like fatty acid elongation and cholesterol formation.

Transaldolase transfers 2-carbon units during the non-oxidative phase.

• Answer: False
  Explanation: Transaldolase transfers 3-carbon units, while transketolase transfers 2-carbon units.

G6PD deficiency can lead to oxidative damage in red blood cells.

Answer: True
Explanation: Insufficient NADPH production impairs the regeneration of reduced glutathione, making red blood cells vulnerable to oxidative stress.

The oxidative phase of the PPP is reversible.

Answer: False
Explanation: The oxidative phase is irreversible, as it involves decarboxylation and NADPH generation, whereas the non-oxidative phase is reversible.

What is the key regulatory enzyme of the PPP?

Answer: Glucose-6-phosphate dehydrogenase (G6PD).

Which molecule provides reducing equivalents for antioxidant defense?

Answer: NADPH.

Name two clinical conditions associated with G6PD deficiency.

Answer: Hemolytic anemia and neonatal jaundice.

What is the primary role of nitric oxide in the body?

Answer: Acts as a vasodilator and signaling molecule.

Which coenzyme is required by transketolase?

Answer: Thiamine pyrophosphate (TPP).