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Question 299
Physiology → Haematology
Classification
Question
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Analysis of platelet granules demonstrates fibrinogen, factor V, factor XIII, PDGF and VEGF in one granule population. Which substance would instead be expected in the other major platelet granule population?
Question Stem
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Options
A
Factor XIII
B
VEGF
C
Fibrinogen
D
Serotonin
E
PDGF
Explanation
The substances listed in the stem belong to platelet alpha granules. dense granules as containing nucleotides, serotonin, phospholipids, calcium and lysosomes. Therefore serotonin belongs to the alternative granule population.
Option Validity
A) Factor XIII is a constituent of alpha granules. It therefore belongs with the substances already described in the stem rather than the dense-granule group.
B) VEGF is an alpha-granule constituent. Dense granules instead contain substances including nucleotides, serotonin, phospholipids and calcium.
C) Fibrinogen is another alpha-granule constituent. It does not distinguish the dense-granule population requested in the question.
E) PDGF is an alpha-granule constituent. Serotonin, rather than PDGF, is found in dense granules.
Further Reading
Saxena. Textbook for MRCOG-1. Physiology - Haematology - Platelets, p.70.