#proteins

• Albuminoid — Resembling albumin or possessing similar properties; an old term given to scleroproteins, a class of insoluble proteins with a structural and supportive role in the organism (such as keratin, collagen, or elastin), found in connective tissues, bones, nails, and hair strands.
• Amide — An organic compound functionally derived from a carboxylic acid where the hydroxyl group (-OH) has been replaced by an amino group (-NH2, -NHR, or -NR2), having the general structural formula R-CO-NR2. Amides are fundamental in nature and industry, forming the peptide bonds that link amino acids into proteins and synthetic polymers like nylon, characterized by high chemical stability due to the conjugation of electrons from the nitrogen atom with the carbonyl group.
• Amino acid — An organic compound with a mixed function, containing in its molecule one or more amino groups (-NH2) and carboxyl groups (-COOH). These structural compounds are the fundamental building blocks of proteins, classified into essential (which cannot be synthesized by the organism and must be provided by diet) and non-essential, playing a crucial role in cellular metabolism, enzyme synthesis, and nerve impulse transmission.