Protein Structure Is Determined by Attractions Between Neighboring Amino Acids

PROTEIN STRUCTURE IS DETERMINED BY ATTRACTIONS BETWEEN NEIGHBORING AMINO ACIDS 

The structure of proteins determines their function and can be described on four levels, illustrated on page 447. The primary structure is the sequence of amino acids in the polypeptide chain. The secondary structure describes how various short portions of a chain are either wrapped into a coil called an alpha helix or folded into a thin pleated sheet. The tertiary structure is the way in which an entire polypeptide chain may either twist into a long fiber or bend into a globular clump. The quaternary structure describes how separate proteins may join to form one larger complex. Each level of structure is determined by the level before it, which means that ultimately it is the sequence of amino acids that creates the overall protein shape. Fhis final shape is maintained both by chemical bonds and by weaker molecular attractions between amino acid side groups. 

Serine (Ser) Threonine (Thr) Cysteine (Cys) Methionine (Met) Glutamic acid (Glu) 

Aspartic acid (Asp) Lysine (Lys) Arginine (Arg) Asparagine (Asn) Glutamine (Gin) 

These 20 amino acids are the building blocks of proteins. The side groups are highlighted in green, and the names printed in red indicate essential amino acids, discussed in Section 13.8. 

Some proteins are hormones that regulate body metabolism and growth. 

Structural proteins are found in skin, hair, and bones. 

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