Chapter 4 - Enzymes

Question 1

What are enzymes?

Answer 1

Biological catalysts that speeds up chemical reactions by providing an alternate pathway of lower Ea and remains chemically unchanged after the reaction.

Question 2

What is the definition of activation energy?

Answer 2

The energy needed to start a chemical reaction.

Question 3

Lock and key hypothesis:
The specific substrate (key) is _______ to the active site of the enzyme (lock) and bind, forming an ________________. The enzyme then _______ the rxn. After rxn, they are no longer _________ to the active site, hence they leave the active site. The enzyme remains ______________ and can accept a new _______.

Answer 3

complementary, enzyme-substrate complex, catalyses, complementary, chemically unchanged, substrate.

Question 4

Characteristics of enzymes?

Answer 4

• is a protein
• specific 3-d structure, only can catalyse one type of rxn
• has an active site that substrate is complementary to
• optimum temp and pH for highest rate of activity

Question 5

What is the effect of increasing temp on enzyme activity?

Answer 5

At optimum temp, kinetic energy of enzyme and substrate molecules increases, increasing chances of collision, forming enzyme-substrate complexes faster. ROR increases until optimum temp, where rate is highest. When temp increase beyond optimum temp, weak bonds within enzymes are broken, causing the enzyme to lose shape of its active site and become denatured. Substrate can no longer fit into active site, hence ROR decreases to 0.

Question 6

What is the effect of pH on enzyme activity?

Answer 6

At pH _, rxn rate is maximum as it is the respective enzyme’s optimum pH. As pH moves further from pH _, rxn rate decreases sharply. When pH moves too far from _, weak bonds within the enzyme are broken, resulting in the lost of shape of the active site and becomes denatured. The substrate can no longer fit into the active site, hence rate decreases sharply until 0.

Question 7

What are the benefits of using enzymes?

Answer 7

• speeds up rxns (save time)
• catalyses reactions at lower temperatures (saves energy)
• specific, so only the intended rxn would occur

Question 8

What is the optimum pH for most enzymes?

Answer 8

pH 7

Question 9

Which enzyme only works at pH 1.5-2.5?

Answer 9

pepsin