Enzymes – Session 2

As we have studied, the enzymes are the biological catalysts. They help to start the chemical reaction by converting the reactants into the products. They speed-up a chemical reaction. But how do these enzymes work to convert the reactants into the products?.

We shall study the mechanism by which the enzymes perform their function. In order to do this, let us first understand the structure of the enzymes. The enzymes are made up of proteins. Proteins are like tiny building-blocks in your body that help you grow, stay healthy, and do lots of important things.

Proteins are made up of tiny parts called the amino acids. Imagine these amino acids as colorful beads that you can string together to make a beautiful necklace. When you string these amino acid beads together in a particular order, you create the protein. It is like making a special necklace with different types and colors of beads.

The enzymes have a special part in their shape called the active site. This part is like a tiny pocket that can hold onto the ingredient. It is a bit like how your hand holds onto a crayon to color a picture. The active site has the power to convert the reactant into product.

The reactant is called the substrate. Suppose you are baking a cake. The ingredients required for making the cake are called the substrates. The enzymes convert the substrates into the products. Let us see how this whole mechanism takes place.

Different substrates have different shapes according to the structure of the enzymes. The substrate comes near the enzyme. The substrate fits into the active site of the enzyme. If the substrate fits into the active site, then the reaction proceeds. Otherwise the reaction does not take place.

When the substrate fits into the active site of the enzyme, the enzyme substrate complex is formed. The active site holds on to the substrate. A connection is formed between the active site and the substrate. This connection is due to the presence of special form of forces between the active site and the substrate. These forces are called the intermolecular forces.

The enzyme catalyzes the reaction. It converts the attached substrate in to the products. Now this enzyme can be reused again. It will convert another substrate into the product. We can say that the enzyme catalyzes the reaction without being used up in the process.

There are two models that explain the mechanism of enzyme action. First is the lock and key model. According to this model, the active site of the enzyme is a rigid structure. Its shape does not change.

This model says that only a specific substrate can fit into the active site of the enzyme. It is like a key fitting into a lock. The substrate acts as the key. The active site acts as the lock. Only a correct key can open the lock. Similarly, only a specific substrate can fit the active site of the enzyme.

The second model is the induced fit model. According to this model, the active site of the enzyme is not a rigid structure. It is slightly flexible. Let us say the shape of the substrate is not fit for the active site. As the substrate attaches to the active site, the active site slightly changes its shape to perfectly fit the substrate.

The enzymes are very specific in nature. Only a specific enzyme can convert the specific substrate into the products. This is due to specific shape of the active site of the enzyme. This shape is specific for the substrate molecules. Different enzymes have different shapes of their active sites.

Different factors effect the activity of the enzymes. One of the most important factor is the temperature. The enzymes work at specific temperature ranges. As we make the temperature rise within the range, the activity of the enzymes increases.

The temperature at which the activity of the enzymes is maximum is called the optimum temperature. For example, enzymes of human body work best at temperature of 37 degrees Celsius. This is the optimum temperature of the enzymes of human body.