What is the function of the protein keratin? a. to provide support and structure for cells in hair, skin, and nails b. to fight infections caused by bacteria and viruses c. to increase chemical reaction rates in the digestive system d. to transmit chemical signals throughout the body

a. to provide support and structure for cells in hair, skin, and nails

Keratin is a structural protein that is present in the epithelial cells of the epidermal layer of the skin, hair, hoofs, feathers and nails. It is also found in the internal organs and glands of animals and humans. It is a protective protein which is less prone to tearing and damage. It is insoluble in water and remains unaffected by the proteolytic enzymes (enzymes which break down proteins). Because of the physically and chemically strong structure of the keratin it supports the structure of the cells of hair, skin and nails.

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.