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

Messenger RNA is made inside the nucleus but translated by ribosomes in the cytoplasm. Which feature of the nuclear envelope accounts for this controlled exchange?

A.Nuclear pores span both membranes and act as regulated gates for selective traffic between nucleoplasm and cytoplasm.
B.The envelope is a single perforated sheet, so everything dissolved in the cytoplasm diffuses freely into the nucleus.
C.Ribosomes docked on the envelope translate RNA before release, exporting only finished proteins.
D.Chromatin threads extend through the envelope, carrying genes outward without any RNA leaving.

Explanation

Core Concept

Nuclear pore complexes span the nuclear envelope and regulate exchange between nucleus and cytoplasm. Large proteins and RNAs generally use signal-dependent transport systems, whereas many small molecules can diffuse through the pores without a targeting signal. This selective transport helps maintain different nuclear and cytoplasmic compositions while permitting continuous exchange.

Correct Answer

ANuclear pores span both membranes and act as regulated gates for selective traffic between nucleoplasm and cytoplasm.

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