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

A macrophage engulfs a bacterium by extending cup-shaped projections that close around the target. Treating the cell with a drug that depolymerizes one cytoskeletal element abolishes this engulfment. Which element does the drug target?

A.Actin filaments, which push the membrane outward around the particle
B.Microtubules, whose sliding lengthens the cell edge
C.Intermediate filaments, which anchor the nucleus during wrapping
D.Centrioles, which rotate to reel the bacterium inward

Explanation

Core Concept

Actin polymerization beneath the attachment site drives pseudopod extension around the bacterium, and coordinated disassembly lets the cup close into a phagosome. Drugs that cap growing filament ends freeze engulfment midway. Microtubules position organelles and intermediate filaments resist tension, but neither builds the protrusive force this feeding mechanism requires.

Correct Answer

AActin filaments, which push the membrane outward around the particle

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