Cell membranes

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called NON-POLAR

Cell membranes are made of PHOSPHOLIPIDs

A Phospholipid

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Phospholipids are important structural components of cell membranes. Phospholipids are modified so that a phosphate group (PO4-) replaces one of the three fatty acids normally found on a lipid. The addition of this group makes a polar "head" and two nonpolar "tails".

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A phospholipid

HYDROPHILIC HEAD

At the other end of the phospholipid is a phosphate group and several double bonded oxygens. The atoms at this end of the molecule are not shared equally. This end of the molecule has a charge and is attracted to water. It is POLAR

HYDROPHOBIC TAILS

The two long chains coming off of the bottom of this molecule are made up of carbon and hydrogen. Because both of these elements share their electrons evenly these chains have no charge. They are NON POLAR. Molecules with no charge are not attracted to water; as a result water molecules tend to push them out of the way as they are attracted to each other. This causes molecules with no charge not to dissolve in water.

3D model of a Phospholipid

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A Phospholipid Bilayer

Phospholipids can form:

BILAYERS

-2 layers of phospholipids with

hydrophobic tails protected inside by the hydrophilic heads.

The PHOSPHOLIPID

BILAYER is the basic

structure of membranes.

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Structure of the cell membrane

Phospholipids

Cell membranes are made mainly of phospholipids. They have:

HYDROPHILIC heads (water liking)

-Attracted to the water POLAR

HYDROPHOBIC tails (water fearing)

-Not attracted to the water NON-POLAR

Phospholipids can form BILAYERS

-2 layers of phospholipids with

hydrophobic tails protected

inside by the hydrophilic

heads.

The PHOSPHOLIPID BILAYER is

the basic structure of membranes.

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Diagram representing the cell membrane Remember the membrane is 7nm wide

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Fluid mosaic model

Cell membranes also contain proteins within the phospholipid bilayer.

This ‘model’ for the structure of the membrane is called the:

FLUID MOSAIC MODEL

FLUID- because individual phospholipids and proteins can move around freely within the layer, like it’s a liquid.

MOSAIC- because of the pattern produced by the scattered protein molecules when the membrane is viewed from above.