Revision: Biomolecules Chemistry Science (English Medium) Class 12 CBSE

Carbohydrates that yield two to ten monosaccharide units, on hydrolysis, are called oligosaccharides.

In the hydrolysis of sucrose, there occurs a change in the sign of optical rotation from dextro (+) to laevo (−). The product so obtained is referred to as invert sugar.

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.

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

Proteins may have one or more polypeptide chains. Each polypeptide in a protein has amino acids linked with each other in a specific sequence and it is this sequence of amino acids that is said to be the primary structure of that protein. Any change in this primary structure, i.e., the sequence of amino acids, creates a different protein.

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.

The repeating monomers in unbranched polymers of nucleic acids are called nucleotides.

A nucleotide is the fundamental unit of nucleic acids, which include DNA and RNA. A pentose sugar, a nitrogenous base, and a phosphoric acid group make up its three constituent parts.

Hormones are chemical messengers created by the endocrine glands and transported through the bloodstream to govern body functions such as development, metabolism, reproduction and mood by interacting with specific target cells.

Organic compounds required in small amounts in the diet to perform specific biological functions are called vitamins.

The unit formed when a nucleoside is linked to phosphoric acid is called nucleotide.

Long chains of nucleotides joined by phosphodiester linkage are called nucleic acids.

Chemical messengers secreted by endocrine glands and transported through blood are called hormones.

Optically active polyhydroxy aldehydes or ketones or the compounds which yield such units on hydrolysis are called carbohydrates.

Carbohydrates which cannot be hydrolysed to simpler units are called monosaccharides.

Carbohydrates which yield two to ten monosaccharide units on hydrolysis are called oligosaccharides.

Carbohydrates which yield a large number of monosaccharide units on hydrolysis are called polysaccharides.

The linkage formed between two monosaccharide units through an oxygen atom is called glycosidic linkage.

The cyclic hemiacetal forms of a sugar differing in configuration at the anomeric carbon are called anomers.

The sequence of amino acids in a polypeptide chain is called primary structure of protein.

Biological catalysts which increase the rate of biochemical reactions are called enzymes.

• Proteins are classified into two types based on their molecular shape: fibrous proteins and globular proteins.
• Fibrous proteins consist of parallel polypeptide chains held together by hydrogen and disulphide bonds; they are generally insoluble in water and provide structural support.
• Globular proteins are formed when polypeptide chains coil into a spherical shape; they are usually soluble in water and perform functional roles such as enzymatic and hormonal activities.
• Protein structure is organized into four hierarchical levels: primary, secondary, tertiary, and quaternary, each representing increasing complexity of folding and organization.
• The stability of higher-level protein structures (secondary, tertiary, and quaternary) is maintained by hydrogen bonds, disulphide linkages, van der Waals forces, and electrostatic interactions.