Current Affairs 11th Class

Category : 11th Class

Molecular weight : Enzymatic proteins are substances of high molecular weight. Bacterial ferredoxin one of the smaller enzymes has molecular weight of 6,000, where as pyruvic dehydrogenase one of the largest-has a molecular weight of 4600000.

Amphoteric nature : Each molecule of enzyme possess numerous groups which yield H+ in slightly alkaline solutions and groups which yield OH- ions in slightly acidic solutions. Unlike many other substances, therefore, the enzymatic protein is amphoteric, i.e., capable of ionizing either as an acid or as a base depending upon the acidity of the external solution.

Colloidal nature : All enzymes are colloidal in nature  and thus provide large surface area for reaction to take place. They posses extremely low rates of diffusion and form colloidal system in water.

Specificity of enzyme : Most of the enzymes are highly specific in their action. A single enzyme will generally catalyze only a single substrate or a group of closely related substrates. The active site possess a particular binding site which complexes only with specific substrate. Thus, only a suitable substrate fulfils the requirements of active site and closely fixes with it.

Heat specificity : The enzymes are thermolabile i.e., heat sensitive. They function best at an optimum temperature \[(20{}^\circ C-40{}^\circ C).\] Their activity decrease with decrease as well as increase in temperature and stops at \[0{}^\circ C\] and above \[80{}^\circ C.\]

Catalytic properties : Enzymes are active in extremely small amounts, e.g., one molecule of invertase can effectively hydrolyze 1,000,000 times its own weight of sucrose. One molecule of catalase is able to catalyze conversion of 5,000,000 molecules of hydrogen peroxide.

Reversibility of reaction : The enzyme-controlled reactions are reversible. The enzymes affect only the rate of biochemical reactions, not the direction. e.g., Lipase can catalyse splitting of fat into fatty acids and glycerol as well as synthesis of fatty acids and glycerol into fats.

\[FatGlycerol+Fatty\text{ }acid\]

pH sensitivity : The enzymes show maximum activity at an optimum pH is \[6-7.05\,\,(7\pm 1.05).\] Their activity slows with decrease and increase in pH till it stops. Each enzyme has its own different favourable pH value.

High efficiency : The effectiveness of an enzymatic reaction is expressed in terms of its turn over number or catalytic centre activity means number of substrate molecules on which one enzymes molecules acts in one minute.

Turn over number depends on the number of active sites of an enzyme. An active site is an area of the enzyme which is capable of attracting and holding particular substrate molecules by its specific charge, size and shape so as to allow the chemical change, Enzymes show 3-D structure. R (alkyl) groups of amino acids from active sites during folding polypeptide chains. Usually 3-12 amino acids form an active site.

Highest turn over number is of carbonic anhydrase (36 million/min or 600000 per second) and lowest is of lysozymes (30/min or 0.5 per second). So carbonic anhydrase is fastest enzyme. The lowest turn over number is of lysozymes.