CBSE Class 12 Chemistry Notes: Surface Chemistry – Enzyme as Catalysts

Enzymes:- Enzymes are defined as the bio-chemical catalysts. Chemically they are globular proteins with higher molar masses ranging from 15000 to 1000,000 g mol^-1

• they catalyses the Biological reactions.

Examples:-

Characteristics of Enzymes:-

1. Specificity:- each enzyme can catalyse only one reaction.
   Ex.
2. Efficiency:-Enzymes are very efficient Catalysts the speed up the rate of reaction by factorof upto 10²⁰.
3. Optimum tempreture and pH:- enzyme catalyzed reactions have maximum rate at physiological pH around 7.4 and human body tempreture of 37^oC (310 K) under atmospheric pressure.
4. Enzyme activators:– the activity of certain enzymes is increased in the presence of certain substances called Co-enzymes.
   For example metal ions Na⁺, Mn⁺² are Co-enzymes.
5. Enzyme inhibitors:- the activity of the enzymes is gets slowed down in the presence of certain substances. Which are called the inhibitors or poisons.

Mechanism of enzyme catalysis:-

Mechanism of enzyme catalyzed reaction is known as lock and key Mechanism.

• Enzymes are highly specific in their action
• There specificity is due to the presence of active sites. The shape of active site of any given enzyme is like acavity such that only a specific substrate can fit into it. In the same way a key fit into a lock.
  –this specific binding leads to the formation of an enzyme substrate – Complex which accounts for high specificity of enzyme catalysed reactions.
• Once the proper orientatation is a attained the substrate molecules reacts to form the product in two steps
• Since product molecule do not have any affinity for the enzyme they leave the enzyme surface making room for fresh substrate.

Step 1: Formation of enzyme substrate Complex

Step 2: Dissociation of enzyme-substrate complex to from product

the rate of the formation of product depends upon concentration of ES.

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