List and explain the main functions of the plasmalemma.

The plasmalemma performs a number of functions, the most important of which are barrier, receptor, and transport.
Barrier function. The cytoplasmic membrane surrounds the cell from all sides, playing the role of a barrier – a barrier between the complexly organized intracellular contents and the extracellular environment.
Receptor function. Proteins are built into the cytoplasmic membrane that are capable of changing their spatial structure in response to the action of various environmental factors and thus transmitting signals into the cell.
Transport function. One of the main functions of the plasmalemma is to ensure the transport of substances both into the cell and from it into the extracellular environment. There are several main ways of transporting substances through the cytoplasmic membrane: simple diffusion, facilitated diffusion, active transport and transport in a membrane package.

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