Cell Membrane: Structure and function
 Plasma (Cell) Membrane: Flexible boundary of a cell that separates a cell from its
surroundings.
 Regulates what enters and leaves the cell and also provides protection and support.

This is called SELECTIVE PERMEABILITY

Some molecules are allowed to pass through plasma membrane at any
time.

Other molecules are only allowed at certain times or in limited
amounts.

Some molecules are never allowed.
 Structure of the Plasma Membrane

The organization of all these structures is called the fluid mosaic model

Plasma membrane contains:


Protein molecules that are embedded in the phospholipid bilayer

Carbohydrate molecules are attached to many of the proteins
Phospholipid Bilayer

Double-layered sheet that makes up nearly all plasma membranes.
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Phospholipid

Lipids with hydrophobic (hates water) tails and
hydrophilic (water lover) heads that form two layers
in the membrane.

Made up of glycerol, 2 fatty acids, and a
phosphate group.

Membrane Proteins


Proteins that can send or receive signals from nearby cells.
Cholesterol

A hydrophobic lipid molecule that changes the fluidity of the
membrane.

Transport or Channel Proteins

Proteins that help carry substances across the membrane or allow
molecules to pass through a channel.

Glycolipid

Lipids with carbohydrate chains that serve as cell recognition
markers.

Glycoprotein

Proteins with carbohydrate chain that cans serve as cell recognition
markers and can help neighboring cells interact or stick to each
other.

Cytoskeleton Filaments

Long protein chains that help the cell hold its shape. Organelles and
other larger molecules can travel along these chains like super
highways in the cell.