Biology: Chapter 5

Question 1

Definition of Enzymes

Answer 1

Proteins that are involved in all metabolic reactions that act as biological catalysts.

Question 2

Why does the human digestive system need to make many different enzymes?

Answer 2

• Enzymes are specific and each enzyme can only speed up the metabolic reaction for one substrate.
• So, the human digestive system needs to make many different enzymes to break down different kinds of substrates.

Question 3

Why is bacteria useful in biotechnology?

Answer 3

• cheaper production
• rapid reproduction

Question 4

How do washing powders remove food stains?

Answer 4

• contains enzymes
• enzymes used to break down and digest the food stains

Question 5

What substrate does amylase break down and what is the product?

Answer 5

starch; maltose/glucose

Question 6

What substrate does liapse break down and what is the product?

Answer 6

fat; fatty acid and glycerol

Question 7

What substrate does protease break down and what is the product?

Answer 7

protein; amino acid

Question 8

What substrate does lactase break down?

Answer 8

lactose

Question 9

What substrate does carbohydrase break down and what is the product?

Answer 9

carbohydrate; starch

Question 10

Definition of Catalysts

Answer 10

A substance that speeds up a reaction without being used up

Question 11

Factors that affect enzyme activity

Answer 11

• temperature
• pH level
• concentration of substrate/enzyme

Question 12

How does temperature affect enzyme activity?

Answer 12

• At low temperature, the enzyme activity is slow because there is lesser kinetic energy.
• As temperature increases, enzyme activity increases as the enzyme and substrate gain kinetic energy.
• At optimum temperature, rate of reaction is the highest because more successful collisions happen. Enzyme can bind to the substrate and catalyse a reaction.
• Beyond optimum temperature, the rate of reaction decreases as the enzyme starts to denature. (active site shape is not complementary to the substrate shape)

Question 13

How do enzymes work?

Answer 13

• Enzyme’s active site shape is complementary to the substrate
• This allows the enzyme to bind to the substrate and form an enzyme-substrate complex.
• The reation is catalysed. Products are formed and released from the enzyme.
• Enzyme is free and ready to catalyse another reaction as it is unchanged and not used up.

Question 14

How does lactose intolerance cause diarrhoea?

Answer 14

• The presence of lactose lowers the water potential inside of the alimentary canal.
• This increases the water potential of the alimentary canal cell lining.
• Thus, water moves from cell lining into the canal, causing diarrhoea.

Question 15

How does pH level affect enzyme activity?

Answer 15

• As pH level increases, the enzyme activity increases.
• At optimum pH, enzyme is the most reactive thus rate of reaction is the highest.
• Beyond optimum pH, the rate of reaction decreases as the enzyme starts to denature.
• Enzyme is not reactive outside of working range.

Question 16

Why are lactase liquids not likely to be successful?

Answer 16

• Lactase might be denatured as digestion of lactose is in the small intestine and the lactase has to go through the stomach, which has a low pH level)
• Lactase works in alkaline conditions
• Protease will break down / digest lactase in the stomach

Question 17

Why do high temperatures increase enzyme activity?

Answer 17

• molecules move faster
• molecules have more kinetic energy
• molecules have more successful collisions.