4. Enzymes

Definition: Enzymes are biological catalysts made of protein which alter the rate of reaction. They remain chemically unchanged at the end of the reactions.

•Enzymes can be produced and used within the cells known as INTRACELLULAR enzymes.

•Enzymes produced in cells but are released out of the cell are known as EXTRACELLULAR enzymes.

Enzymes increase the speed of chemical reactions within living cells by reducing their activation energy. As the activation energy (or energy barrier of the reaction) can be overcome, reaction occurs more quickly.

Figure above - Presence of enzymes reduce the activation energy of the reaction.

For enzyme-catalysed reactions to occur,

(1) Enzyme and substrate molecules must collide.

(2) Collision between enzyme and substrate molecules must be at the correct orientation.

(3) Enzymes and substrates must collide with sufficient energy equal or greater than activation energy.

Naming of enzymes

qAn enzyme is named by attaching the suffix “-ase” to the name of the substrate on which it acts.

qEgs of enzymes:

Carbohydrase, protease, lipase.

Guess which substance does each enzyme act on?

Specific enzymes

1. Carbohydrase

2. Protease

3. Lipase