Mode Of Action Of Enzymes


Mode Of Action Of Enzymes

Mode Of Action Of Enzymes


This unit aims to understand what are enzymes and how they function inside the body.


Enzymes are globular proteins. They are also called biological catalysts as they speed up chemical reactions. Thus, substrates are converted into products faster.

Active Site

The site present in enzymes where the substrate binds and forms the enzyme-substrate complex.

The R group present in the enzyme reacts with the substrate to ensure maximum binding.

Activation Energy

The additional amount of energy required to convert substrate into product.

The enzyme speeds up a chemical reaction by lowering the activation energy.

Types Of Enzymes

There are two types of enzymes based n the site where they perform their actions.

1) Intracellular

Enzymes which are present inside the cell are called intracellular.

2) Extracellular

Enzymes which are present outside the cell.

Enzyme Specificity:

Key And Lock Model

According to the key and lock model, the shape of the active site of the enzyme and substrate are complementary.

They fit with each other completely to form a complex.

It works like a key and lock. As only the right key can fit in the lock. In the same way, only the right substrate can fit into the enzyme.

This shows the specific nature of enzymes.

Induce Fit Model

According to induce fit model the shape of the active site of the enzyme and substrate are not complementary to each other.

Instead when the substrate is present the active site continuously shapes itself so that the substrate can fit into it.

Thus, the enzyme adjusts itself like gloves on hands. This model is currently more acceptable.

Investigating Progress Of Enzyme Catalysed Reaction

Progress of reactions catalyzed by the enzyme can be followed by two methods:

1) Rate of formation of product

2) Rate of disappearance of substrate

1) Rate of formation of product (oxygen):

H2O2--catalase---à H2+O2

The reaction is catalyzed by the catalase enzyme. The product formed here is oxygen and hydrogen.

In this reaction, we have to follow how fast oxygen is being formed.

Here are the steps which need to be followed.

Mashup some biological material like potato tubers. Mix it with water and then filter the solution. The result will be a solution containing catalase.

Add this catalase to H2O2 in a test tube.

Collect the gas formed in a gas syringe.

Record volume after every minute.

2) Rate Of Disappearance Of Substrate (Starch)

Starch---amylase---------à maltose

Add amylase solution to starch suspension present in a test tube.

Take samples of the reacting solution after a regular time interval.

Test the sample for the presence of starch with Iodine in KI.

If starch is present iodine solution will turn dark blue.

When starch starts breaking down the color lightens.

When no starch is present the color is orange-brown.

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