Revision: Class 12 >> Biomolecules NEET (UG) Biomolecules

Carbohydrates are optically active polyhydroxy aldehydes or polyhydroxy ketones or compounds that can be hydrolysed to polyhydroxy aldehydes or polyhydroxy ketones.

Chemically proteins are polyamides which are high molecular weight polymers of the monomer units, i.e., α-amino acids. OR It can also be defined as proteins are the biopolymers of a large number of α-amino acids and they are naturally occurring polymeric nitrogenous organic compounds containing 16% nitrogen and peptide linkages (-CO-NH-)

Enzymes are biological catalysts that speed up chemical reactions in living cells without being consumed in the process.

The bond that connects α-amino acids to each other is called a peptide bond.

α-Amino acids are carboxylic acids having an amino (–NH₂) group bonded to the α-carbon, that is, the carbon next to the carboxyl (–COOH) group.

Amino acids that cannot be synthesised in the human body and must be obtained through diet are known as essential amino acids.

An ∝-amino acid molecule contains both acidic carboxyl (-COOH) group as well as basic amino (-NH₂) group. Proton transfer from acidic group to basic group of amino acid forms a salt, which is a dipolar ion called zwitter ion.

Chemically, peptide linkage is an amide formed between the –COOH group and –NH₂ group. The reaction between two molecules of similar or different amino acids proceeds through the combination of the amino group of one molecule with the carboxyl group of the other. This results in the elimination of a water molecule and the formation of a peptide bond –CO–NH–. The product of the reaction is called a dipeptide because it is made up of two amino acids.

For example, when the carboxyl group of glycine combines with the amino group of alanine, we get a dipeptide, glycylalanine.

Denaturation is the process in which the secondary and tertiary structure of a protein is disrupted due to heat, a change in pH, or chemicals, while the primary structure remains unchanged. In denaturation, peptide bonds are not broken; only the weak bonds (like hydrogen bonds) are disturbed.

A nitrogenous base is an organic molecule (purine or pyrimidine) that carries genetic information in nucleic acids.

The unit formed by joining the anomeric carbon of the furanose (sugar) with a nitrogen of a base is called nucleoside.

Nucleic acids are large biological macromolecules that store and transmit genetic information in living organisms.

DNA is a double-stranded nucleic acid that stores and transmits hereditary information and can replicate itself.

RNA is a single-stranded nucleic acid that helps in protein synthesis and information transfer.

A nucleotide is the basic structural unit of nucleic acids, composed of a nitrogenous base, a pentose sugar, and a phosphate group.

A nucleoside consists of a nitrogenous base linked to a pentose sugar without a phosphate group.