Glucose-6-phosphate dehydrogenase (G6PD) deficiency renders erythrocytes susceptible to haemolysis under oxidative stress. G6PD is critical because it is the ONLY source of which protective molecule in RBCs?

• A NADH, which drives the methemoglobin reductase reaction
• B NADPH, which maintains glutathione in its reduced (GSH) form ✓
• C ATP, which powers Na+/K+-ATPase membrane integrity
• D 2,3-BPG, which regulates haemoglobin oxygen affinity

Explanation

Mature red blood cells lack mitochondria and nuclei, making the pentose phosphate pathway (HMP shunt) the exclusive source of NADPH via G6PD. NADPH is required by glutathione reductase to regenerate reduced glutathione (GSH) from oxidised GSSG. GSH detoxifies peroxides via glutathione peroxidase. G6PD deficiency leaves RBCs unable to regenerate GSH; exposure to oxidants (primaquine, dapsone, fava beans, infections) overwhelms the cells, denaturing haemoglobin (Heinz bodies) and causing haemolysis.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.