Nutrition: Proteins
Nutrition: Proteins

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Nutrition: Proteins

1.6 Protein shapes and functions

1.6.1 Introduction to shapes and functions

Although a protein may be composed simply of a single long chain of amino acids, it does not remain as an elongated string, but folds up into a very precise shape. The three-dimensional shape of most proteins consists of a mixture of these different arrangements. However, unlike a piece of string, each molecule of the protein is, in fact, folded into precisely the same shape and that shape is crucial to its correct functioning in the body.

Figure 5
Figure 5 Structure of collagen, an important component of skin, tendons, bone and many other tissues. A collagen molecule is a triple helix, composed of three polypeptide chains, which are themselves helical, coiled around each other
Figure 6
Figure 6 Structure of myoglobin, a protein that binds to oxygen molecules in muscles. The black dots, some of which are numbered, are the amino acids and the red disc is the oxygen-binding group. The ‘folded sausage’ shows the overall shape of the protein. Note that numbering always goes from the amino (‘left hand’) end to the carboxyl (‘right hand’) end of a protein, and this reflects the order in which the amino acids are put together when the protein is made by a cell
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