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

A mouse cell and a human cell are fused after their surface proteins are tagged with different fluorescent antibodies. Right after fusion the two colors occupy separate halves, but after forty minutes at body temperature they are intermixed. What does this result support?

A.New proteins were synthesized during the wait and spread evenly across the surface
B.Antibodies carry membrane fragments back and forth between the two cell halves
C.Membrane proteins drift laterally within the bilayer rather than staying fixed in place
D.Cell fusion triggers wholesale replacement of the plasma membrane

Explanation

Core Concept

Intermixing of the two labels shows that proteins anchored in the mouse and human halves migrated across the merged membrane surface. Such migration requires lateral diffusion of proteins through the fluid lipid bilayer, the central claim of the fluid mosaic model. Chilling the fused cells prevents the mixing, confirming that bilayer viscosity governs the movement.

Correct Answer

CMembrane proteins drift laterally within the bilayer rather than staying fixed in place

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