1) They serve as enzymatic catalysts, are used as
transport molecules (hemoglobin transports oxygen) and storage molecules (iron is stored
in the liver as a complex with the protein ferritin)
2) they are used in movement (actin, myosin )
3) they are needed for mechanical support (skin and
bone contain collagen-a fibrous protein)
4) they mediate cell responses (rhodopsin is a
protein in the eye which is used for vision)
5) antibody proteins are needed for immune
protection; control of growth and cell differentiation uses proteins (hormones).
