Proteins are critical components of all tissues of the human body. Like carbohydrates and fats,
they contain carbon, hydrogen and oxygen. Unlike the other macronutrients, they contain
nitrogen and their structure is dictated by DNA.
The building blocks of proteins are amino acids. The amine group of the amino acid contains
nitrogen. The portion of the amino acid that changes, giving each amino acid its distinct identity,
is the same chain. The body cannot make essential amino acids so we must obtain them from our
diet. Our body can make non-essential amino acids from parts of other amino acids,
carbohydrates and fats.
Amino acids bind together to form proteins. Genes regulate the amino acid sequence, and thus
the structure, of all proteins. The shape of a protein determines its function. When a protein is
denatured by damaging substances, such as heat and acids, it loses its shape and its function.
When a particular amino acid is limiting, protein synthesis cannot occur. A complete protein
provides all nine essential amino acids. Mutual supplementation combines two complementary
protein sources to make a complete protein.
In the stomach, hydrochloric acid denatures (uncoils) proteins and converts pepsinogen to
pepsin; pepsin breaks protein into smaller polypeptides and individual amino acids. In the small
intestine, proteases break polypeptides into smaller intestine break the smaller peptide fragments
into single amino acids, which are then transported in the bloodstream to the liver for distribution
Proteins serve many important functions, including (1) enabling growth, repair, and maintenance
of body tissues; (2) acting as enzymes and hormones; (3) maintaining fluid and electrolyte
balance; (4) maintaining acid-base balanc