Q1. Source: CSIR NET NOV 20; Session I
Some metabolic aspects of the Red Blood Cell (RBC) are proposed in the following statements:
A. Synthesis of fatty acids does not occur in the RBC
B. The pentose phosphate pathway is operative in the RBC
C. RBC cannot synthesis reduced glutathione (GSH)
D. RBC does not contain enzyme like adenosine deaminase and pyrimide nucleotidase
E. NADH-dependent methemoglobin reductase system is present in RBC
Which one of the following combinations is not correct?
a. A and B
b. B and C
c. C and D
d. D and E
Statement Analysis
A. True. Mature red blood cells lack a nucleus and mitochondria. As a result, they cannot synthesize fatty acids, allowing more space for hemoglobin and efficient oxygen transport.
B. True. The pentose phosphate pathway (PPP) is active in RBCs and is the only pathway that generates NADPH, which protects the cell against oxidative damage.
C. False. RBCs can synthesize reduced glutathione (GSH). GSH acts as a major antioxidant, protecting hemoglobin and the cell membrane from reactive oxygen species.
D. False. RBCs contain enzymes such as adenosine deaminase (ADA) and pyrimidine nucleotidase (P5’N). ADA functions in the purine salvage pathway, while pyrimidine nucleotidase removes pyrimidine nucleotides generated during RNA degradation as erythrocytes mature.
E. True. The NADH-dependent methemoglobin reductase system continuously converts methemoglobin back to functional hemoglobin, ensuring efficient oxygen transport.
Therefore, the incorrect statements are C and D.
Correct Answer: c. C and D
Q2. Source: CSIR NET NOV 20; Session I
Which one of the following causes constriction of blood vessel?
a. Carbon monoxide
b. Nitric oxide
c. Endothelin-I
d. Atrial natriuretic peptide
Statement Analysis
Blood vessel diameter is regulated by molecules that either relax or contract vascular smooth muscle.
- Carbon monoxide (CO) acts as a vasodilator, relaxing blood vessels.
- Nitric oxide (NO), produced by endothelial cells, is a potent vasodilator that increases blood flow and lowers blood pressure.
- Endothelin-I is one of the most powerful endogenous vasoconstrictors. It binds to ETₐ receptors on vascular smooth muscle cells, increasing intracellular calcium levels and causing the muscles to contract, thereby narrowing the blood vessel.
- Atrial natriuretic peptide (ANP) also promotes vasodilation and helps reduce blood pressure.
Hence, the correct answer is: c. Endothelin-I
Revision Box
Red Blood Cell Metabolism
- Pentose Phosphate Pathway (PPP) = Produces NADPH to protect RBCs from oxidative damage.
- Reduced Glutathione (GSH) = Major antioxidant that maintains RBC integrity.
- NADH-dependent Methemoglobin Reductase = Converts methemoglobin back into functional hemoglobin.
- Mature RBCs lack a nucleus and mitochondria, so they cannot synthesize fatty acids.
Blood Vessel Regulation
- Nitric Oxide (NO) = Vasodilator
- Carbon Monoxide (CO) = Vasodilator
- Atrial Natriuretic Peptide (ANP) = Vasodilator
- Endothelin-I = Potent vasoconstrictor
Your Score?
2/2 – Animal Physiology Expert!
1/2 – Great effort! Keep revising.
0/2 – Time to brush up on your concepts.
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