B1.1.7 Glycoproteins

glycoprotein

membrane proteins with a carbohydrate chain attached found on the other surface of the cell membrane

describe the structure of glycoproteins

• made up of a protein backbone

• covalently attached carbohydrate chain faces outwards

• highly hydrophilic

where are glycoproteins found?

• found on the outer surface of cells on the membrane

• in granules

• extracellular matrix

• golgi apparatus or ER

function of glycoproteins

• cell recognition - helps immune system identify cell types

• cell signaling - acts as receptors for hormones, neurotransmitters, etc.

• cell adhesion - helps cells stick together in tissues

• structure & protection - carbohydrate chain protects from damage

role of glycoproteins in cell-to-cell recognition

• carbohydrate chains act as name tags that help cells recognize each other

• white blood cells detect foreign glycoproteins to fight infections

• some glycoproteins act as receptors to receive signals from other cells

• glycoproteins detect ABO blood type so body knows which blood is compatible

antigen

foreign substances that trigger an immune response - can be proteins, polysaccharides, etc., can be recognized by glycoproteins

antibodies

made by immune system, recognizes + binds to + neutralizes antigens - produced by plasma, must fit exactly to the antigen

why is it important for RBCs to have glycoproteins on their membrane?

the carbohydrate chains act as markers, which identify blood group, allowing the immune system to distinguish self from non-self

ABO blood groups

• A: A-antigens on RBCs, anti-B antibodies in plasma

• B: B-antigens on RBCs, anti-A antibodies in plasma

• AB: A + B antigens on RBCs, no antibodies in plasma

• O: no antigens on RBCs, anti-A+B-anti antibodies in plasma

how do antibodies recognize and neutralize antigens?

each antibody has a specific binding site that is complementary to a specific part of an antigen - when shape matches, antibody binds to the antigen and identifies it as “non-self” + triggers response

which blood type is known as “universal donors” and why?

O blood group

• no antigens - doesn’t trigger immune response for recipient, not attacked when donated

• O can only receive from O - the two antibodies would attack any other blood group other than its own since O has no antigens to attack

which blood type is known as “universal recipients” and why?

AB blood group

• have both A and B antigens - triggers immune response to all other recipients but does not attack received blood types

• can receive blood from any blood group but can only donate to AB - has both A and B antigens that all other blood groups have antibodies to attack