Chapter 4: Enzymes

Question 1

What are enzymes

Answer 1

• biological / organic catalysts
• a substance that can speed up a chemical reaction without it being chemically changed at the end of the reaction
• made out of protein molecules that are folded to take on 3-D globular shape

Question 2

Types of Enzymes

Answer 2

1. Carbohydrases
2. Lipases
3. Proteases

Question 3

What reactions do enzymes catalyses

Answer 3

• some are involved in digestion to break apart large molecules into smaller and simpler substances so that they are soluble in water and diffuse through the cell membrane
• some are also involved in biological reactions
• enzyme catalysed reactions include reactions that build up complex substances as well as reactions that break down complex substances
• it catalyses all chemical reactions that occur in an orgnaism
• they are also only produced when they are needed

Question 4

Lock-and-key hypothesis

Answer 4

1. An enzymes has a specific 3-D shape. It has a depression called “active sit”
2. Only substrate with shape complementary to active site can fit into enzyme. When substrate binds to enzyme, enzyme substrate complex is formed and the enzyme is the lock and the substrate is the key
3. While the substrate is attached to active site, chemical reaction occurs and substrate is converted into products
4. Products leave active site and the enzyme remains unchanged and catalyses another reaction

Question 5

Characteristics of enzymes

Answer 5

1. Enzymes speed up chemical reaction
2. Enzymes are specific in action
3. Enzymes are required in minute amounts and remains unchanged at the end of the reaction
4. Enzymes are affected by temperature
5. Enzymes are affected by pH

Question 6

How do enzymes speed up chemical reactions

Answer 6

• providing an alternative pathway with a lower activation energy required to start a chemical reaction
• speeds up rate of reaction by lowering activation energy

Question 7

How are enzymes specific in action

Answer 7

• they have active sites
• only substrates with a shape complementary to the active site can fit into the enzyme
• when enzyme binds to substrate, an enzyme-substrate complex is formed
• high temp, alkali & acid can affect shape of enzyme and its function

Question 8

Why are enzymes only required in minute amounts and remains unchanged at the end of the reaction

Answer 8

• they are very efficient molecules
• remains unchanged in the reaction they catalyse 👉 the same enzyme molecules can be reused
• hence only a small amount of enzymes can catalyse reaction for large amount of substrate

Question 9

How enzymes are affected by temperature

Answer 9

1. enzyme is less active at low temp since KE of molecules is low 👉 rate of collisions is low
2. As temp increases, rate of reaction increases since KE of molecules increases 👉 rate of collision increases
3. The enzyme is most active at optimum temp
4. Increasing temp above optimum causes a rapid decrease in the rate of enzyme reaction since the active site begins to lose its shape & is not longer complementary to substrate
5. In the end, all the enzymes will all denature as temp increases

Question 10

How enzymes are affected by pH

Answer 10

• some work best in acidic, alkaline or neutral solutions
• when enzymes are in pH conditions that vary from optimum, they start to denature
• extreme pH changes denatures enzymes