<prompt> Alpha helix is which structurePrimarySecondaryTertiaryQuaternary  <response>: Ans. b SecondaryStructural organization of amino acid can be of following types: Primary structure: Linear sequence of amino acid, held together by peptide bond a type of covalent bond. Secondary structure: Folding of short 3-30 residue, contiguous segment of polypeptide. Joined together by non-covalent bond primarily. Hydrogen bond: Most important bond Vander walls force Hydrophobic bond Electrostatic bond Tertiary structure: 3D conformation of polypeptide. Bonds are non-covalent similar to secondary structure Quaternary structure: When more than one polypeptide aggregate to form one functional protein. The spatial relationship between these polypeptide subunit is called quaternary structure. Bonds are non-covalent similar to secondary structureAlpha Helix It is an example of secondary structure. It is the most common and stable secondary structure. Right handed spiral Each turn of alpha helix is formed by 3.6 amino acyl residues. Size of 1 turn of alpha helix: 0.54 nm Proteins whose major secondary structure is alpha-helix: Hemoglobin and Myoglobin 