7.1: What are proteins? Proteins are defined, and their basic classification and the importance of their structure in their functions are described. 7.2: Amino acids Amino acids found in proteins, their classification, acid-base properties, and sources are described. 7.3: Primary structure of proteins Peptide bond, disulfide bond, their nomenclature, and their characteristics, along with the primary structure of proteins and their importance, are described. 7.4: Secondary structure of proteins Secondary structures of proteins, including alpha-helix, beta-pleated sheets, random coils, and triple helix, are described. 7.5: Tertiary structure of proteins The tertiary structure of proteins and interaction, including disulfide bonds, salt bridges, coordinate covalent bonds, hydrogen bonding, and hydrophobic interaction, are described as responsible for forming and maintaining the tertiary structure of proteins. 7.6: Quaternary structure of proteins The quaternary structure of proteins and its need are described. 7.7: Summary of protein structure levels The structure levels of proteins are described and illustrated. 7.8: Protein misfolding and denaturation Misfolding of proteins, medical problems associated with the misfolding, and denaturation of proteins are described. 7.9: Enzymes Terminology related to enzymes, their nomenclature, and classification are described along with the models of enzyme action, factors that affect enzyme activity, and inhibitors that retard or destroy the enzyme activity.