Apentix/AP Biology/Unit 2: Cell Structure and Function/Question
AP Biologyhardmcq1 pt

After an LDL particle reaches an early endosome, its receptor releases the cargo and recycles back to the cell surface. Which feature of the endosome accounts for cargo release?

A.Clathrin reenters the endosome and pries the ligand off its receptor
B.Dynamin constricts around the receptor and mechanically strips bound cargo
C.Proton pumps acidify the endosomal interior, changing receptor shape so LDL detaches
D.ATP driven motors pull the ligand out of the vesicle into the cytosol

Explanation

Core Concept

V type ATPases load protons into the endosome until the lumen sits near pH 5 to 6. That acidity alters the conformation of the LDL receptor and weakens ligand binding, freeing the receptor to bud into recycling tubules while LDL stays behind for degradation. Experimental drugs that neutralize endosomal pH block this handoff and trap ligands aboard their receptors.

Correct Answer

CProton pumps acidify the endosomal interior, changing receptor shape so LDL detaches

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