Biomolecules And Enzymes Revision Notes For NEET

BIOMOLECULES AND ENZYMES

 

        Biomolecules are the organic molecules present in living organism made up of H, O, C and N in different proportions. They are further classified into biomacromolecules (proteins, nucleic acids, lipids and polysaccharides) and biomicromolecules (amnio acids and fatty acids).

        Living tissue is composed of two pools-acid soluble pool, which represents cytoplasmic composition and acid insoluble pool, which represents cytoplasmic and organelle composition.

        Carbohydrates are represented by molecular formula CnH2nOn and defines as polyhydroxy aldehydes or ketone compounds, which on hydrolysis give aldehydes or ketones. Broadly, they are classified into-monosaccharides, oligosaccharides and polysaccharides.

        Amnio acids are made up of C, H, N, O and sometimes sulphur too and they serve as monomers of proteins. Each amnio acids has a free carboxyl group, amino group and a side chain. Broadly amino acids are classified into-alcoholic, aromatic, heterocyclic and sulphur containing.

        Zwitter ion is a molecule containing positive and negative ionic groups. Amino acid can act as acid and base as it contains one amino and one carboxylic group. When put in a neutral solution amino acid exists as dipolar ion or zwitter ion.

        Isoelectric point is the pH at which amnio acid is electrically neutral or exists as Zwitter ion.

        Proteins are the linear, unbranched polymers of amino acids which are linked together via peptide bond. They can be simple (albumins, globulins and prolamins) or conjugated (glycoproteins and diploproteins), structurally, they are classified into primary, secondary, tertiary and quaternary.

        Lipids are hydrophobic compounds made up of long chain of fatty acids with carboxyl group. They can be simple (fats and waxes), compound (phospholipids, glycolipids and chromolipids) or derived (sterols and prostaglandins).

        Nucleic acids constitute the genetic material. DNA and RNA are present in all living cells. The basic unit that forms them is nucleotides, which is made up of phosphoric acid, pentose sugar and a nitrogenous base. Structure of DNA was given by Watson and Crick.

        ATP or Adenosine Triphosphate forms the energy currency of the cell. It was discovered by Karl Lehmann in 1929.

        Enzymes are proteinaceous substances capable of altering the rate of chemical reactions without undergoing any changes in themselves. They are also known as biological catalyst. They work by lock and key mechanism or induced fit mechanism.

        Activation energy is defined as the amount of energy required by substrate molecules to form the product.

        Active site is a distinct cavity in which substrate is bound and active centre of enzyme is present. Here, the amino acids are grouped together to combine with the substrate.

        Lock and key hypothesis proposed that geometry of active sites of enzyme and shape of substrate molecule are complementary to each other. This theory explains the specificity of enzyme action.

        Activity of enzyme is affected by many factors such as temperature, pH, ionic concentration, E-S concentration and product concentration.

        Inhibitors are specific chemicals which when binds to an enzyme shuts off the enzymic activity and this process is called inhibition. It can be competitive or non-competitive.

        Proenzymes are the precursor of a proteolytic enzyme. They are cleaved to form an active enzyme. Other name for proenzymes is zymogen.

        Induced fit hypothesis proposed that active site of enzyme doesn’t initially exist in a shape complimentary to the substrate. Rather, it is induced to assume the complementary shape as the substrate become bound to enzyme.

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