Biology

Enzymes are protein molecules that act as the biological catalysts. A 

catalyst is a molecule which can speed up chemical reaction but 

remains unchanged at the end of the reaction. Enzymes catalyze most of 

the metabolic reactions which take place within a living organism. 

They speed up the metabolic reactions by lowering the amount of energy 

needed to activate the reacting molecules. They are specific that 

usually act on only one type of substrate, so each of them just 

perform one particular reaction. Enzymes can catalyze both anabolic and catabolic reactions within an 

organism. That means by the interaction between the side-chains of the 

enzyme and the atoms of the substrate, the enzyme can encourage the 

formation or breaking of bonds in a substrate molecule. Each enzyme possesses an active site. The active site is a region of 

enzyme which allows a substrate to bind with it. The configuration of 

the active site gives the specificity of enzyme. That means the active 

site and the substrate should be exactly complementary so that the 

substrate can fit in perfectly. Once they collide, the substrate and 

some of the side-chains of the enzyme’s amino acids form a temporary 

bond so that the substrate can be held in the active site. They 

combine to from an enzyme-substrate complex and the enzyme can start 

its work. It is called the “lock and key” hypothesis. (Lock: enzyme, 

key: substrate) .

Catalase is an enzyme found in both plant and animal cells. It catalyzes the decomposition of 

hydrogen peroxide into water and oxygen: 2H2O2 Catalase 2H2O + O2 .

The more substrate molecules there are available, the more often one 

will bump into the active site of an enzyme, so the more rapidly they 

will be converted to product. Therefore, increasing substrate 

concentration increases the rate of reaction. At high substrate concentrations, 

each enzyme will be working as fast as it can, with substrate 

molecules virtually ‘queuing up’ for...