biological membranes and ion channels

Biological membranes

Lipids and proteins

Non covalent assemblies

• Asymmetric
• Fluid mosaic structure
• Charged

Polar lipids fatty acids: saturated, unsaturated (PUFA)

Lipases

Lipases break ester/amide/phosphate bonds between backbone and fatty acids/sugars.

Phospholipids

Phospholipids are lipids which contain phosphate, and they can have glycerol or sphingosine as backbone. In both cases the C1 is linked to a phosphate.

Glycolipids

Glycolipids can also have a glycerol or sphingosine backbone, but the phosphate is not there. The sugar is directly linked to the C of the backbone.

Cholesterol

Cholesterol 27C

If cholesterol is inserted in a well-packed membrane, it disturbs the hydrophobic interaction between the fatty acids and increases fluidity. If cholesterol is inserted in a not-so-packed membrane, it increases the hydrophobic interactions and increases rigidity. For most membranes, this results in a more rigid structure.

Structure and fluidity

Polar lipids form bilayer (fatty acids → micelles).

Fluidity is affected by temperature, length, saturation, and cholesterol content.