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There are a total of 20 different types of amino acids that combine together to make proteins.

Proteins are large, specialized, and complex molecules which include oxygen, carbon, nitrogen, hydrogen, and sometimes sulfur. Proteins are composed of thousands of smaller units known as amino acids which are attached together to form a long chain of polypeptides (proteins). There are a total of 20 different types of amino acids that combine together to make proteins. These amino acids are identical but have different side chains. The amino acid sequence of proteins determines the unique 3- dimensional structure of each protein and its specific function. The function of the protein in the human body is that it is required for the structure, regulation, and function of the tissues and organs of the body. [Image Will be Uploaded Soon]

The structure of a protein is a 3-dimensional arrangement of amino acid residues that link-up to form polypeptide chains. Proteins are polymers whose structure is formed by link-up of several such long chains that are made from amino acid (monomer of protein)  sequences. The position and property of amino acids decide the ultimate structure and function of the protein. [Image Will be Uploaded Soon] Amino acids are substituted methane, in which the alpha-carbon valencies are occupied by a carboxyl group (-COOH), amino group (-NH2), hydrogen, and a variable R-group. A variety of amino acids are present depending on the R-group, out of which 20 are used in the making of the polypeptide chain. The structure of a protein is better described by using its types.

[Image Will be Uploaded Soon] The primary protein structure is simply a linear polypeptide chain made up of the sequence of amino acids. Changing even a single amino acid position as there are limited amino acids monomers i.e 20 presents in the human body will result in alteration of the 3-dimensional structure of the protein which further leads to different chains and finally a different protein. This simple sequencing of protein by amino acids is called its primary structure. For example, Human insulin has two polypeptide chains, A and B.

[Image Will be Uploaded Soon] The secondary structure is the local folded structures formed by interactions (hydrogen bond) between atoms of the polypeptide chain except for atoms of the R-group. This causes the chain to fold or coil and affect the 3-D shape of a protein in two different conformations known as α-helix and β-pleated sheets. Both the structure results due to the hydrogen bonds, which forms between the amino H atom of one amino acid and the carbonyl O of another.

There can be other numerous functional groups that can be linked to each protein like carboxylic acid, alcohols, carboxamides, etc. These functional groups are also responsible for affecting protein folding and its function.

[Image Will be Uploaded Soon] The final 3-dimensional shape of a polypeptide is called protein tertiary structure. The tertiary structure is mainly due to repulsive and attractive forces of different R-groups of amino acids which make up a protein. The secondary interactions that are seen in the tertiary structure include ionic bonding, hydrogen bonding, London-dispersion, dipole-dipole interactions. R-groups that are polar in nature form hydrogen bonds and dipole-dipole interactions. Similarly, R-groups with opposite charges form the ionic bonds. Non-polar hydrophobic R-groups assemble together within the protein. Disulfide bond also contributes to tertiary structure, by covalent linking between the cysteine chain’s sulfur-containing side. By keeping polypeptide parts to attach firmly to each other, they act as “Molecular safety-pins”.

[Image Will be Uploaded Soon] Multiple polypeptide chains that are linked together to form certain proteins are called subunits. The orientation and arrangement of subunits which come together with multi-subunits to give the quaternary structure of proteins. Proteins and other macromolecules present in the body interact to form such complex assemblies. These assemblies are required because protein can develop specialized functions in them that stand alone. Proteins are unable to perform transmission of cell signals and carrying out DNA replication. Its example includes:

Proteins are called building blocks of the body because they are found in abundance throughout the body. They account for 20% total weight of the body and are important for all the functions of the body. They are recruited in all the reactions that are biochemical in nature, taking place inside the cell. Growth and development of the body, making of new cells, repairing damaged cells and tissues all depend upon proteins. Proteins are also present in food like milk, pulses, and egg, etc. It is also present in nails and hairs.

Functions of Protein in the Human Body are:

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