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PLASMA MEMBRANE

Describe how a cell’s plasma membrane functions.

Identify the roles of cholesterol, carbohydrates, and proteins in
the plasma membrane.
OBJECTIVES

The plasma membrane is a thin, flexible boundary between a cell
and its environment.

The selective permeability of the membrane allows some
materials through and keeps others out.

Phospholipids are responsible for this property.
FUNCTION OF THE PLASMA MEMBRANE

The plasma membrane is composed of a phospholipid bilayer.

Phospholipid heads are polar and hydrophilic.

Phospholipid tails are non-polar and hydrophobic.

The tails face inward, and the heads face outward.

Water soluble substances cannot pass through the non-polar
region of the membrane, thus making the membrane selectively
permeable.
PLASMA MEMBRANE STRUCTURE

Transport proteins span through the membrane and move
needed substances into and out of the cell.

Cholesterol maintains the fluidity of the plasma membrane.

Carbohydrates stick out of the outer layer of the plasma
membrane and help identify chemical signals and act as a
recognition mechanism.
COMPONENTS OF THE PLASMA MEMBRANE

The fluid mosaic model of the plasma membrane allows
components to move along the phospholipids, sliding past each
other in constant motion.
FLUID MOSAIC MODEL