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Question 333
Physiology → Haematology
Classification
Question
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An erythrocyte is transporting carbon dioxide from peripheral tissues. Which intracellular reaction is directly facilitated by an enzyme contained within the erythrocyte?
Question Stem
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Options
A
Conversion of fibrinogen to fibrin
B
Conversion of prothrombin to thrombin
C
Gamma-carboxylation of coagulation factors
D
Polymerisation of fibrin monomers
E
Combination of carbon dioxide with water to form carbonic acid
Explanation
Erythrocytes contain carbonic anhydrase. This enzyme catalyses the combination of carbon dioxide with water to produce carbonic acid and therefore contributes to the erythrocyte's role in respiratory-gas transport.
Option Validity
A) Conversion of fibrinogen to fibrin is mediated by thrombin during coagulation and is not the reaction catalysed by erythrocyte carbonic anhydrase.
B) Prothrombin is converted to thrombin by prothrombin activator in the presence of calcium.
C) Gamma-carboxylation concerns vitamin K-dependent coagulation factors rather than carbon dioxide transport by erythrocytes.
D) Fibrin monomer polymerisation occurs during clot formation and is unrelated to erythrocyte carbonic anhydrase.
Further Reading
Saxena R. Textbook for MRCOG-1. Chapter 3: Physiology – Haematology. p.67.