Cell-Cell Recognition

Glycoproteins and glycolipids are components of the plasma membrane

Carbohydrates and polypeptides can combine via covalent bonds to make glycoproteins

Oligosaccharides project outwards from the membrane

The carbohydrate is attached either to protein in the membrane (glycoprotein) or to lipid (glycolipids)

Interactions between the oligosaccharides and carbohydrate-binding proteins in adjacent cells allow cell-cell recognition

Oligosaccharides in adjacent cells can become linked binding them into a tissue

Cells can recognise foreign cells or infected body cells by the oligsaccharides of their glycoproteins and glycolipids

ABO Glycoproteins

Red blood cells carry different glycoproteins in their membranes

Glycoproteins can act as antigens which can identify cells

An individual's blood type is determined by the glycoprotein antigens on the surface of their red blood cells.

Blood type A individuals = type A glycoprotein antigens

Blood type B individuals = type B glycoprotein antigens

Blood type AB individuals = both types of glycoprotein antigens

Blood type O = individuals have neither

Glycoproteins are important in recognition and blood transfusions

A person with blood group A has components of the defence system (antibodies) which recognise blood cells from a person with blood group B as foreign.

All other blood groups are able to donate blood to an individual with blood type AB, because they don't have antibodies

Blood group O is called the universal donor because they have no glycoproteins on their cells.