Enzymes

Question 1

Explain enzyme action in terms of the “lock-and-key” hypothesis.

Answer 1

• An enzyme has a specific 3-d shape, which contains an active site.
• Only the substrate (the key) with a 3-d shape complementary to that of the active site can fit into the enzyme (the lock) to form an enzyme-substrate complex.
• Chemical reactions will then occur and the substrate is converted into products.

Question 2

Explain the effects of temperature on the rate of enzyme catalyzed reactions.

Answer 2

• Enzymes are inactive at very low temperatures. The kinetic energy is low at low temperatures, hence, the chances of substrate molecules colliding with enzymes are very low.
• As the temperature rises, enzyme activity increases. The rise in temperature increases the kinetic energy of molecules, increasing the chance of collision between substrate and enzyme molecules. This increases the rate of formation of enzyme-substrate complex.
• The optimum temperature is the point when the rate of reaction is the highest and the enzyme is the most active.
• Beyond the optimum temperature, the enzyme activity decreases. High temperatures breaks the bond within the enzyme and changes its 3-d shape. The active site of the enzyme loses its original shape and the enzyme is denatured.

Question 3

Explain the effects of pH on the rate of enzyme catalyzed reactions.

Answer 3

Different enzymes have different optimum pHs at which they are most active. Extreme changes in pH denature the enzyme and cause it to lose function.

Question 4

Explain the mode of action of enzymes (in terms of an active site, enzyme-substrate complex, lowering of activation energy and enzyme specificity.) wow what a big chunk of words that i dont understand.

Answer 4

• An enzyme has a specific 3-d shape, which contains an active site.
• Only the substrate (the key) with a 3-d shape complementary to that of the active site can fit into the enzyme (the lock) to form an enzyme-substrate complex.
• i.e. amylase helps to speed up digestion of only starch, not proteins
• Enzymes lower the activation energy needed to start a chemical reaction.