The Function of Proteins

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The Function of Proteins

Proteins are complex organic molecules which contain carbon, hydrogen, oxygen, nitrogen and sometimes sulphur. They have many functions around the human body.

Proteins generally have one or more unbranched polypeptide chains attached 2 them, which are made up of amino acid monomers that are held together by peptide bonds. Although this sounds relatively simple, the shape of a protein is actually complex and 3D and can sometimes have a quaternary structure.

The primary structure of a protein consists of different amino acids arranged in a chain in a specific order. The secondary structure links the chains together using hydrogen bond, ionic bonds, covalent bonds, Van der Waals forces and disulphide bonds. The tertiary structure involves the folding of the secondary structure into a complex specific 3D shape. The optional quaternary structure combines two or more tertiary polypeptide structures together.

Proteins are usually put into two different groups according to their structural appearance – fibrous proteins and globular proteins. Fibrous proteins have a secondary structure that is vital as it is made of alpha-helix or beta-pleated sheets. On the other hand, globular proteins have a tertiary structure that is important as is it bent and folded into a 3D spherical shape. Another difference is that fibrous proteins are insoluble in water, whereas globular proteins are soluble in water. Examples of fibrous include keratin and collagen and examples of globular proteins include enzymes (amylase, globulins and insulin), antibodies and hormones. There are also other types of proteins such as simple proteins (albumen, globulins, histones and scleroproteins) and conjugated proteins that have a non-protein group imbedded inside them (glycoproteins, nucleoproteins, chromoproteins and flavoproteins).

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The first function of proteins is that they can be used for movement animal bodies. Myosin and Actin are filamentous protein molecules contained in muscles. Movement is achieved in the presence of calcium ions because myosin and actin will slide past each other and form a “cross-bridge” structure which contracts the muscle. Muscles are vital in animals as they work with bones to allow movement.

Proteins are also used in other structural ways, such as in the composition of skin, hair and cartilage. Collagen is one protein that is important in skin, hair and in connective tissues in general ...

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