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Question 526
Biochemistry → General
Classification
Question
SSBAQuestion Header
A hydrolytic enzyme destined for intracellular degradation is synthesised normally. Which sequence most accurately describes its subsequent route to an active degradative organelle?
Question Stem
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Options
A
Free ribosome → peroxisome → phagosome → primary lysosome
B
Rough endoplasmic reticulum → Golgi apparatus → primary lysosome → secondary lysosome after fusion with a phagosome
C
Smooth endoplasmic reticulum → mitochondrion → Golgi apparatus → secondary lysosome
D
Nucleolus → rough endoplasmic reticulum → peroxisome → secondary lysosome
E
Golgi apparatus → rough endoplasmic reticulum → mitochondrion → primary lysosome
Explanation
Lysosomal proteins are synthesised by ribosomes attached to rough endoplasmic reticulum and subsequently processed through the Golgi apparatus. Primary lysosomes are Golgi-derived inactive vesicles. Fusion of a primary lysosome with a phagosome produces the active secondary lysosome in which degradation occurs.
Option Validity
A) Lysosomal proteins are not synthesised by free ribosomes or routed through peroxisomes.
C) Smooth endoplasmic reticulum and mitochondria do not provide this lysosomal protein-trafficking route.
D) The nucleolus and peroxisomes are not sequential components of lysosomal enzyme trafficking.
E) This reverses the rough endoplasmic reticulum-to-Golgi sequence and incorrectly includes mitochondria.
Further Reading
Richa Saxena. Textbook for MRCOG-1: Basic Sciences in Obstetrics & Gynaecology. Biochemistry and Nutrition — Biochemistry — Rough endoplasmic reticulum, Golgi apparatus and lysosomes. Printed pages 125–126.