Cell surface membrane structure

What is the fluid mosaic model and who composed it and when did they compose it?

• in 1972, Singer and Nicolson, proposed a model that allowed the passage of molecules through the membrane, which explained how cell membranes could be more dynamic and interact more with the cells environment

What is the cell surface membrane made of?

• Glycoproteins

• Glycolipids

• Cholesterol

• Extrinsic proteins

• Intrinsic proteins

What is the role of glycolipids and glycoproteins?

Glycolipid:

• Attached to lipid by glycosidic bond.

• Cellular recognition

Glycoprotein:

• Attached to protein.

• Receptors for cell signalling

What is the role cholesterol?

• It controls the fluidity of the cell surface membrane as the temperature changes

• When the temperature increases, phospholipids drift due to an increase in kinetic energy. This means the bilayer is now more fluid which causes the bilayer to have more gaps and holes where substances are able to move through. And so cholesterol causes the phospholipids to get closer and become more tightly packed so the permeability becomes normal again

What are some roles of the cell surface membrane?

• Compartmentalisation - Separates the cell’s components from its external environment

• Controls transport of substances in and out of the cell

• May contain enzymes involved in specific metabolic pathways

• Cell recognition - Has antigens, so that the organisms immune system can recognise it and not attack it

• .Cell signalling - May release chemicals that signal to other cells

• Contains receptors for chemical signals and so it is a site for cell communication and signalling; hormones and drugs may bind to membrane bound-receptors

• May be a site of chemical reactions