Apentix/AP Biology/Unit 2: Cell Structure and Function/Question
AP Biologyeasymcq1 pt

Some ribosomes float free in the cytosol while others attach to the rough endoplasmic reticulum. How do these two populations compare?

A.They are structurally identical pools whose products differ in destination, sorted by signal sequences.
B.Free ribosomes replicate DNA while bound ones translate mRNA, splitting replication from expression.
C.Free ribosomes operate only in prokaryotes and attached ones only in eukaryotes.
D.The two classes read different genetic codes, giving secreted proteins unusual sequences.

Explanation

Core Concept

Free and rough-ER-bound ribosomes are structurally the same type of ribosome. Proteins that lack an ER-targeting signal are generally synthesized on free cytosolic ribosomes, whereas proteins destined for secretion, the plasma membrane, or the endomembrane-system lumen are translated on ribosomes recruited to the rough ER. Many proteins used in the nucleus and mitochondria are synthesized on free ribosomes and imported after translation.

Correct Answer

AThey are structurally identical pools whose products differ in destination, sorted by signal sequences.

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