Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues. The sequence of amino acids in a protein is defined by the sequence of a gene, which is encoded in the genetic code. In general, the genetic code specifies 20 standard amino acids; however, in certain organisms the genetic code can include selenocysteine - and in certain archaea - pyrrolysine. Shortly after or even during synthesis, the residues in a protein are often chemically modified by posttranslational modification, which alters the physical and chemical properties, folding, stability, activity, and ultimately, the function of the proteins. Sometimes proteins have non-peptide groups attached, which can be called prosthetic groups or cofactors. Proteins can also work together to achieve a particular function, and they often associate to form stable protein complexes.
Functions of Protein for Human Body
Protein has a range of essential functions in the body, including the following:
  • Required for building and repair of body tissues (including muscle)
  • Enzymes, hormones, and many immune molecules are proteins
  • Essential body processes such as water balancing, nutrient transport, and muscle contractions require protein to function
  • Protein is a source of energy
  • Protein helps keep skin, hair, and nails healthy
  • Protein, like most other essential nutrients, is absolutely crucial for overall good health
  • Antibodies defend the body from germs
  • Contractile proteins are responsible for movement
  • Enzymes speed up chemical reactions
  • Storage proteins store amino acids