NCERT Solution Class 11th Biology Chapter – 9 Biomolecules Notes

NCERT Solution Class 11th Biology Chapter – 9 Biomolecules

NCERT Solution Class 11th Biology Chapter – 9 Biomolecules

?Chapter – 9?

✍Biomolecules✍

?Notes?

Although there is a bewildering diversity of living organisms, their chemical composition and metabolic reactions appear to be remarkably similar.

The elemental composition of living tissues and non-living matter appear also to be similar when analyzed qualitatively.

The most abundant chemical in living organisms is water. There are thousands of small molecular weight (<1000Da) biomolecules.

Amino acids, monosaccharide and disaccharide sugars, fatty acids, glycerol, nucleotides, nucleosides, and nitrogen bases are some of the organic compounds seen in living organisms.

There are 21 types of amino acids and 5 types of nucleotides. Fats and oils are glycerides in which fatty acids are esterified to glycerol. Phospholipids contain, in addition, a phosphorylated nitrogenous compound.

Only three types of macromolecules i.e., proteins, nucleic acids, and polysaccharides are found in living systems.

Lipids, because of their association with membranes separate in the macromolecular fraction. Biomacromolecules are polymers. They are made of building blocks that are different. Proteins are heteropolymers made of amino acids.

Nucleic acids (RNA and DNA) are composed of nucleotides. Biomacromolecules have a hierarhy of structures i.e., primary, secondary, tertiary and quaternary structures.

Nucleic acids serve as genetic material. Polysaccharides are components of the celt wall in plants, fungi and also of the exoskeleton of arthropods.

They also are storage forms of energy (e.g. starch and glycogen.) Proteins serve a variety of cellular functions. Many of them are enzymes, some are antibodies, some are receptors, some are hormones and some others are structural proteins.

Collagen is the most abundant protein in the animal world and Rubisco is the most abundant protein in the whole biosphere.

Enzymes are proteins that catalyze biochemical reactions in the cells. Ribozymes are nucleic acids with catalytic power.

Proteinaceous enzymes exhibit substrate specificity, require optimum temperature and pH for maximal activity. They are denatured at high temperatures.

Enzymes lower the activation energy of reactions and enhance greatly the rate of the reactions.

Nucleic acids carry hereditary information and are passed on from parental generation to progeny.

Biomolecules – All the carbon compounds that we get from living tissues can be called ‘biomolecules’.

a-amino acids – Amino acids are organic compounds containing an amino group and an acidic group as substituents on the same carbon i.e., the a-carbon. Hence they are called a-amino acids.

Nucleosides – Some of these are nitrogen bases-adenine, guanine, cytosine, uracil, and thymine. When found attached to a sugar, they are called nucleosides.

Primary metabolites – In animal tissues, one notices the presence of all such categories of compounds. These are called primary metabolites.

Secondary metabolites – When one analyses plant, fungal and microbial cells, one would see thousands of compounds other than these called primary metabolites, e.g., alkaloids, flavonoids, rubber, essential oils, antibiotics, coloured pigments, scents, gums, spices. These are called ‘secondary metabolites.

Biomacromolecules – One, those which have molecular weights less than one thousand and are usually referred to as macromolecules or simply as biomolecules while those which are found in the acid-insoluble fraction are called macromolecules or as biomacromolecules.

Glycogen – Animals have another variant called glycogen.

Deoxyribonucleic acid/ Ribonucleic acid – A nucleic acid containing deoxyribose is called deoxyribonucleic acid (DNA) while that which contains ribose is called ribonucleic acid (RNA).

Quaternary structure – The manner in which these’ individual folded polypeptides or subunits are arranged with respect to each other is the architecture of a protein otherwise called the quaternary structure of a protein.

Phosphodiester – The bond between the phosphate and hydroxyl group of sugar is an ester bond. As there is one such ester bond on either side, it is called the phosphodiester bond.

Metabolic pathway – A multistep chemical reaction when each of the steps is catalyzed by the same enzyme complex or different enzymes is called a metabolic pathway.

Isomerases – Includes all enzymes catalyzing the interconversion of optical, geometric, or positional isomers.

Ligases – Enzymes catalyzing the linking together of 2 compounds e.g., enzymes that catalyze joining of C-O, C-S, C-N, PO, etc. bonds.

Substrate – The chemical which is converted into a product is called a ‘substrate’.

Inhibition/Inhibitor –  When the binding of the chemical shuts off enzyme activity, the process is called inhibition and the chemical is called an inhibitor.