Protein Structure Proteins are formed by linking the amine nitrogen of one amino acid with a carbon atom on another amino acid, and then repeating this “peptide bond” to make a chain dozens or hundreds of amino acids long The carbon-nitrogen backbone of the protein molecule forms a sort of zigzag pattern, with the “side groups” — the other atoms on each amino acid — sticking out to the sides The Protein Helix One effect of the peptide bond is a certain kind of regularity that causes the molecule as a whole to twist and form a spiral, or helix Very few proteins exist as a simple regular helix, but those that do tend to join together in strong fibers These include connective-tissue collagen in meat, an important factor in its tenderness, and the source of gelatin (pp 130, 597) Protein Folds The other influence on protein structure is the side groups of its amino acids Because the protein chain is so long, it can bend back on itself and bring together amino acids that are some distance along the chain from each other Amino acids with similar side groups can then bond to each other in various ways, including via hydrogen bonds, van der Waals bonds, ionic bonds (p 813), and strong covalent bonds (especially between sulfur atoms) This bonding is what gives a particular protein molecule the characteristic shape that allows it to carry out its particular job The weak, temporary nature of the hydrogen and hydrophobic bonds allows it to change its shape as it works The overall shape of a protein can range from a long, extended, mostly helical molecule with a few kinks or loops, to compact, elaborately folded molecules that are called “globular” proteins Collagen is an example of a helical protein, and the various proteins in eggs are mainly globular ... various ways, including via hydrogen bonds, van der Waals bonds, ionic bonds (p 813), and strong covalent bonds (especially between sulfur atoms) This bonding is what gives a particular protein molecule the characteristic...bend back on itself and bring together amino acids that are some distance along the chain from each other Amino acids with similar side groups can then bond to each other in various ways, including via hydrogen bonds,... shape that allows it to carry out its particular job The weak, temporary nature of the hydrogen and hydrophobic bonds allows it to change its shape as it works The overall shape of a protein can range from a long, extended, mostly helical molecule with a few