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Proteins

Proteins are large, complex molecules that play many critical roles in the body. They do most of the work in cells and are required for the structure, function, and regulation of the body’s tissues and organs. Each protein has unique functions. Proteins are essential components of muscles, skin, bones and the body as a whole.

Proteins are made up of hundreds or thousands of smaller units called amino acids, which are attached to one another in long chains, in a specific order determined by the base sequence of nucleotides in the DNA coding for the protein. There are 20 different types of amino acids that can be combined to make a protein. The sequence of amino acids determines each protein’s unique 3-dimensional structure and its specific function.

Examples of proteins include whole classes of important molecules, among them enzymes, hormones, and antibodies.

Proteins are one of the three types of nutrients used as energy sources by the body, the other two being carbohydrate and fat. Proteins and carbohydrates each provide 4 calories of energy per gram, while fats produce 9 calories per gram.

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