What Role Do Proteins Play in the Human Body

Much of the structure and function of our body is based on proteins. Thus, protein and individual amino acids must function in our body in a number of ways. For instance, proteins can function as:

  • enzymes (regulate chemical reactions)
  • structural proteins (yield form to cells and tissue)
  • contractile proteins (provide basis for muscle contraction)
  • antibodies (help protect us from foreign entities)
  • transport proteins (help transport substances in our blood)
  • protein hormones (insulin, glucagon, and growth hormone)
  • clotting factors (allow our blood to clot to stop a hemorrhage)
  • receptors on cells (allow hormones and neurotransmitters to function)

Individual amino acids can be used to make certain hormones and neuro-transmitters such as epinephrine, serotonin, norepinephrine, and thyroid hormone (Table 6.2). In fact, most neurotransmitters are derived from amino acids. Amino acids are also used to make other important substances such as creatine, choline, carnitine, nucleic acids, and the vitamin niacin. Last, amino acids can be used by some tissue as an energy source or can be converted to glucose or fat depending upon our current nutritional/metabolic state (that is, fasting, fed, exercise).

Proteins Are the Basis of Our Structure and Function 129 Table 6.2 Select Substances Made from Amino Acids

Amino Acid Substances Made From the Amino Acid(s)

Tryptophan Serotonin

Lysine and methionine Carnitine

Methionine, glycine and arginine Creatine

Aspartic acid and glutamine Pyrimidines

Aspartic acid, glutamine and Purines glycine

Tyrosine or phenylalanine Epinephrine, norepinephrine, thyroid hormone, dopamine

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