TOP

3. Enzymes

3.1 What are enzymes?
1 . Enzymes:

  • They are biological catalysts made of protein. They alter the rate of chemical reactions without themselves being chemically changed at the end of the reaction.

Catalysts are substances that can change the speed of a chemical reaction.

3.2 Characteristics of enzymes & Factors affecting enzyme activity.

1 . Characteristics of enzymes:

  • They alter or speed up the rates of chemical reactions that occur in a cell.
  • They remain unchanged after a chemical reaction.
  • They are specific.→”Lock & Key” hypothesis (One enzyme act on one substrate)
  • They are affected by temperature.
  • They are affected by pH.
  • They may need other enzymes to work (Coenzymes).
  • They catalyse reversible reactions

2 . Factors affecting enzyme activity:

1) Temperature

Fig. 3.1 Effect of temperature.

A) The enzyme activity is increasing from its inactive state as the temperature increases.

B) The enzyme is at its most active state at optimum/optimal temperature (the temperature of which enzyme is most active).

C) The enzyme activity decreases as it is exposed to temperature above the optimum/optimal temperature. And at extreme temperature, the enzyme stopped because they are denatured.

2) pH

Fig. 3.2 Effect of pH.

A) The enzyme activity is increasing from its inactive state as the pH (acidity/alkalinity) increases.

B) The enzyme is at its most active state at optimum/optimal pH (optimum acidity/optimum alkalinity).

C) The enzyme activity decrease when it is exposed to above the optimum/optimal pH. And at extreme pH (too acidic/too alkaline), the enzyme stopped because they are denatured.

D) Most enzymes work best at neutral pH.

E) Some enzymes work best at acidic pH.

F) Some enzymes work best at alkaline pH

 

No comments yet.

Leave a Reply