Apentix/AP Biology/Unit 2: Cell Structure and Function/Question
AP Biologymediummcq1 pt

In a mutant cell line, lysosomal hydrolases never receive their mannose 6 phosphate tags in the Golgi. Where do these enzymes end up?

A.Retained permanently in the rough ER where they were synthesized
B.Secreted outside the cell, because untagged lysosomal proteins follow the default secretory route
C.Delivered to lysosomes anyway through general membrane affinity
D.Imported into mitochondria via their signal sequences

Explanation

Core Concept

Mannose 6 phosphate marks hydrolases for receptors that divert them into vesicles bound for lysosomes. Lacking the tag, the enzymes escape sorting at the trans Golgi network and ride default traffic to the cell surface. Lysosomes stay enzyme poor while extracellular fluid fills with hydrolases, the signature pattern of inclusion cell disease.

Correct Answer

BSecreted outside the cell, because untagged lysosomal proteins follow the default secretory route

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