In the quaternary structure of a protein the polypeptide is folded through the mechanism of amino acids rotating around bonds and folding into a alpha-helix or beta-pleated sheet structure and stabilized by bonds. amino are the building blocks of proteins. They are made up of a center carbon atom bound to a positively charged group and a negatively charged group and a side chain. In the secondary structure of a protein the amino acid side chains of the folded polypeptide interact, forming a complex three-dimensional shape. primary structure formed by amino reactions link amino acids together, forming a linear chain. The of a protein exists if multiple polypeptides bind together to form a functional protein.

Structure of amino acid-It is made up of compounds containing carbon, nitrogen, oxygen, and hydrogen. In an amino acid, the positively charged amino group and the negatively charged carboxyl group are attached to the same carbon atom (alpha carbon). The 22 amino acids differ from one another because of the side chain attached to the central carbon atom. The central carbon atom is also attached to the H atom.

Proteins have four levels of structural organization-

Primary structure
Secondary structure
Tertiary structure
Quaternary structure

Quaternary structure-It is made up of two or more polypeptide chains. Each polypeptide chain is called a subunit. The polypeptide chains in the quaternary structure of a protein can be similar or different. The polypeptides are stabilized by noncovalent bonds such as hydrophobic interactions, hydrogen bonds, and electrostatic interactions. For example-Hemoglobin.

The answers for the blanks are-

1.Noncovalent, 2.amino, 3.carboxyl, 4. quaternary structure

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