CBSE Class 12-science Answered

Biochemistry refers to four distinct aspects of a protein's structure:

• Primary structure - the amino acid sequence of the peptide chains.
• Secondary structure - highly regular sub-structures (alpha helix and strands of beta sheet) which are locally defined, meaning that there can be many different secondary motifs present in one single protein molecule.
• Tertiary structure - three-dimensional structure of a single protein molecule; a spatial arrangement of the secondary structures. It also describes the completely folded and compacted polypeptide chain.
• Quaternary structure - complex of several protein molecules or polypeptide chains, usually called protein subunits in this context, which function as part of the larger assembly or protein complex.