Proteins are..for the growth and rebuilding of....,but they can also be utilized as a(n)...of energy . In some diets,such as the diet of the eskimo,they from the main source of energy.proteins are frist broken down into amino acids then they are...into the blood and pass around the body. Amino acid not used by the body are eventually excreted in the urine in the from of urea. Proteins unlike carbohydrates and fats,cannot be...for future use.