An Account of Proteins and their Structure

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An Account of Proteins and their Structure

It is difficult to describe in a simple sentence the role of proteins. Let’s say:

When there is something to do, it is a protein that does it.

 Some examples of proteins 

  • Antibodies: they recognize molecules of invading organisms.
  • Receptors: part of the cell membrane, they recognize other proteins, or chemicals, and inform the cell.
  • Enzymes: assemble or digest.

The role (or function) of a protein depends on its shape, and chemical formula.

Proteins play a number of vital roles in all organisms. Unlike carbohydrates and lipids they always contain nitrogen as well as carbon, hydrogen and oxygen. Sulphur is often present.

The building blocks of the proteins are amino acids. Proteins are made of a long chain of amino acids, sometimes modified by the addition of sugars and phosphates. Amino acids unite to form proteins in much the same manner the monosaccharides combine to form polysaccharides, and fatty acids and glycerol combine to form fats and oils. This happens when two amino acids reacts. The reaction occurs between the amino group of one amino acid and the carboxyl group of another. To make this happen a condensation reaction has to occur which involves the removal of a molecule of water. Once this happens two amino acids become joined by a peptide link to form a dipeptide. To form a polypeptide a series of condensation reactions must happen which forms a longer chain. The individuality of a particular protein is determined by the sequence of amino acids comprising its polypeptide chains, together with the pattern of folding and cross-linkages.

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The primary structure is the sequence of amino acids, which form a chain connected by . The amino acid sequence of a protein determines the higher levels of structure of the molecule. A single change in the primary structure (the amino acid sequence) can have a profound biological change in the overall structure and function.

The secondary structure is the way a small part, saptially near in the linear sequence of a protein folds up into:

  the first structure described by Linus Pauling. It has a rod shape. The peptide is coiled around an imaginary ...

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