Proteins

Recall that organic acids contain a −COOH group and organic bases, or amines, contain an −NH₂ group. There is one substituted hydrocarbon that contains both groups. An amino acid is a compound that contains both carboxyl and amino functional groups in the same molecule. There are about 20 amino acids that your body needs to function.

Your cells can manufacture some, but not all, of the amino acids. For example, your body can make glycine, but not phenylalanine. The essential amino acids that your body cannot make must come from foods like those in Figure 17.

Figure 17 The foods shown are all good protein sources. Classifying Group the foods into three or four categories.

Your cells use amino acids as the monomers for constructing protein polymers. A protein is a polymer in which at least 100 amino acid monomers are linked through bonds between an amino group and a carboxyl group. The instructions for making proteins are stored in DNA. Proteins make up the fibers of your muscles, your hair and fingernails, and the hemoglobin in your blood. Your body may contain as many as 300,000 different proteins.

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