A distinct purple colour develops without heating (Figure . a and b). Figure . (a): Biuret test Figure .
(b): Colour intensity increases with increase in concentration The more the distance between the sulphur atoms, the more the proteins bend; the more the hair curls. . Enzymes Enzymes are globular proteins that catalyse the many thousands of metabolic reactions taking place within cells and organism. The molecules involved in such reactions are metabolites.
Metabolism consists of chains and cycles of enzyme-catalysed reactions, such as respiration, photosynthesis, protein synthesis and other pathways. These reactions are classified as • anabolic (building up of organic molecules). Synthesis of proteins from amino acids and synthesis of polysaccharides from simple sugars are examples of anabolic reactions. • catabolic (breaking down of larger molecules).
Digestion of complex foods and the breaking down of sugar in respiration are examples of catabolic reactions (Figure . ). Figure . : Enzyme reaction Enzymes can be extracellular enzyme as secreted and work externally exported from cells.
Eg. digestive enzymes; or intracellular enzymes that remain within cells and work there. These are found inside organelles or within cells. Eg.
insulin. - - . . PM specially formed pocket in the enzyme – the active site , this is called lock and key mechanism of enzyme action.
As the enzyme and substrate form a ES complex , the substrate is raised in energy to a transition state and then breaks down into products plus unchanged enzyme (Figure . ). Figure . : Enzyme mechanism Substrate Enzyme Enzyme Product Enzyme - Substrate complex .
. Enzyme Cofactors Many enzymes require non-protein components called cofactors for their efficient activity. Cofactors may vary from simple inorganic ions to complex organic molecules. They are of three types: inorganic ions, prosthetic groups and coenzymes (Figure .
). • Holoenzyme – active enzyme with its non protein component. • Apoenzyme – the inactive enzyme without its non protein component. .
. Properties of Enzyme • All are globular proteins. • They act as catalysts and effective even in small quantity. • They remain unchanged at the end of the reaction.
• They are highly specific. •