The arrangement of phospholipids, proteins and carbohydrates in the fluid-mosaic model of membrane structure.

The fluid mosaic model is the name for the cell-surface membrane and all the stuff in it; it is knows as fluid because the things in it can move around.

Phospholipids

The phosphate group is attracted to water (hydrophilic), where as the other end of fatty acids are not (hydrophobic)- this means that phospholipids will form a layer on water:

Phospholipids come together so that their tails are facing in and their heads facing out in contact with water. This is called a phospholipid bilayer and is what the cell-surface membrane is made of.

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Proteins

Intrinsic proteins go from one side of the bilayer through to the other. Some are enzymes and others are protein channels which carry substances across the membrane.

Extrinsic proteins are embedded in but do not span the membrane. Some act as structural support; others join with glycolipids to be receptors.

Intrinsic right, extrinsic left:

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Carbohydrates

Carbohydrates bond with lipids and proteins to form receptors. The carbohydrate branch acts as a recognition site in glycoproteins, as does the whole glycolipid, to detect chemicals like hormones and toxins.

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