Can proteins in the plasma membrane move around the membrane? Why is this characteristic beneficial to the cell?

Yes they can

Explanation:

Based on the fluid mosaic model of the lipidic bilayer of the membranes we know that proteins embedded in it have the ability to undergo translational diffusion. Membrane fluidity is important to the cell because is associated to transport rates, it can respond to the necessities of the organism, for example, in some organisms this fluidity can be modified by temperature stress or according to their nutrient necessities.

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