Structure of protein- Protein is made up of 20 naturally occurring amino acids. A typical amino acid contains a amino and a carboxyl group attached to the central α-carbon atom (Figure 38.3). The side chain attached to the α-central carbon atom determines the chemical nature of different amino acids. Peptide bonds connect individual amino acids in a polypeptide chain. Each amino acid is linked to the neighboring amino acid through a acid amide bond between carboxyl group and amino group of the next amino acid. Every polypeptide chain has a free N-and C-terminals (Figure 38.3). Primary structure of a protein is defined as the amino acid sequence from N- to the C-terminus with a length of several hundred amino acids. The ordered folding of polypeptide

Figure 38.3: The connection between two adjacent amino acids in a polypeptide.

chain give rise to the 3-D conformation known as secondary structure of the protein such as helices, sheet and loops. Arrangement of the secondary structure gives rise to the tertiary structure. α-helix and β-sheet are connected via unstructured loops to arrange themselves in the protein structure and it allows the secondary