Essay On Proteins

Proteins are considered to be the most versatile macromolecules in a living system. This is because they serve crucial functions in all biological processes. Proteins are linear polymers, and they are made up of monomer units that are called amino acids. The sequence of the amino acids linked together is referred to as the primary structure. A protein will spontaneously fold up into a 3D shape caused by the hydrogen bonding of amino acids near each other. This 3D structure is determined by the sequence of the amino acids. The 3D structure is referred to as the secondary structure. There is also a tertiary structure, which is formed by the long-range interactions of the amino acids. Protein function is directly dependent on this 3D structure.

An alpha amino acid is made up of a central carbon atom, or the alpha carbon, which is linked to an amino group, a carboxylic acid group, a hydrogen atom, and a distinct R group, called the side chain. There are twenty different kinds of side chains that vary in shape, hydrogen-bonding capacity, chemical reactivity, charge, size, and hydrophobic character that are typically found in proteins. All proteins in all species are made up of the same set of twenty amino acids, with a few exceptions. In order to classify amino acids, the molecules are assorted in four groups on the basis of the general characteristics of their R groups. The four groups are hydrophobic amino acids with nonpolar R groups, polar amino acids with neutral R groups but the charge is not evenly distributed, positively charged amino acids with R groups that have a positive charge at physiological pH, and lastly, negatively charged amino acids with R groups that have a negative charge at physiological pH. The simplest amino acid is glycine because it has only a single hydrogen atom as its side chain. Alanine is the next simplest amino acid because it has a methyl group as its side chain. Seven of the twenty amino acids have side chains that are readily ionizable and they are able to accept or donate protons to facilitate reactions and form ionic bonds. Amino acids are typically abbreviated to a three-letter, which are typically the first three letters

A polypeptide chain is a series of amino acids that are joined by the peptide bonds. Each amino acid in a polypeptide chain is called a residue. It also has polarity because its ends are different. The backbone or main chain is the part of the polypeptide chain that is made up of a regularly repeating part and is rich with the potential for hydrogen-bonding. There is also a variable part, which comprises the distinct side chain. Each residue of the chain has a carbonyl group, which is good hydrogen-bond acceptor, and an NH group, which is a good hydrogen-bond donor. The groups interact with the functional groups of the side chains and each other to stabilize structures. Proteins are polypeptide chains that have 500 to 2,000 amino acid residues. Oligopeptides, or peptides, are made up of small numbers of amino acids. Each protein has a precisely defined, unique amino acid sequence, referred to as its primary structure. The amino acid sequences of proteins are determined by the nucleotide sequences of genes because nucleotides in DNA specify a complimentary sequence in RNA, which specifies the amino acid sequence. Amino acid sequences determine the 3D structures of proteins. An alteration in the amino acid sequence can produce disease and abnormal function. All of the different ways