Chapter 04 - Enzymes

Question 1

Define enzymes

Answer 1

Enzymes are proteins that function as biological catalysts. They catalyse/speed up the rate of chemical reactions while remaining chemically unchanged at the end of the reaction

Question 2

What is a catalyst?

Answer 2

A substance that speeds up a chemical reaction without chemically changing at the end of the reaction

Question 3

What is activation energy?

Answer 3

The minimum amount of energy required to initiate a chemical reaction

Question 4

What is the relationship between activation energy and the rate of a chemical reaction?

Answer 4

The lower the activation energy, the faster the reaction

Question 5

What do enzymes do to activation energy?

Answer 5

Enzymes lower activation energy - allows chemical reactions to occur more effeciently

Question 6

What do enzymes break down?

Answer 6

Enzymes break down complex substances into simpler and smaller substances. In digestion, substances are broken down to become soluble in water and small enough to diffuse through cell membranes (Catabolic)

Question 7

What do enzymes build up?

Answer 7

Enzymes build up/synthesises complex substances from simpler ones (Anabolic)

Question 8

Name 2 examples of digestive enzymes

Answer 8

1) Starch —-> (amylase) —-> Maltose
2) Maltose —-> (maltase) —-> Glucose
3) Protein —-> (protease) —-> Polypeptides —-> (protease) —-> Amino Acids
4) Fats —-> (lipase) —-> glycerol and 3 fatty acids

Question 9

Describe an example of enzymes building up/synthesising complex substances from simpler substances

Answer 9

1) Amino acids are taken into cells to build up proteins. Cells contains special enzymes to catalyse the reactions
2) Enzymes synthesise glucose from carbon dioxide and water during photosynthesis

Question 10

Describe an example enzymes breaking down complex substances into simpler substances

Answer 10

1) Catalase breaks down hydrogen peroxide a toxic substance in water and oxygen cells. Protects cell from harmful effects which can damage cell parts. Catalase is found in many cells to detoxify harmful substances
2) In cellular respiration, enzymes are involved in chemical reactions to break down glucose in order to release energy
3) In digestion, enzymes catalase the process of breaking down large insoluble food molecules into small and soluble substances to pass through the cell membrane

Question 11

Enzymes ____ all reactions and are only ____ when needed

Answer 11

Enzymes catalyse all reactions and are only produced when needed (e.g digestive enzymes produced when food needs to be digested)

Question 12

Enzymes are ____ in their action

Answer 12

Enzymes are specific in their action (e.g amylase only breaks down starch)

Question 13

Why are enzymes specific in their action?

Answer 13

1) Enzymes only work on a specific type of substrate molecule due to the enzymes specific shape at the active site
2) Only a substrate with complementary shape will fit into the active site
3) Only one type of substrate will bind to the active site

Question 14

Describe the process of an enzyme catalysing a reaction

Answer 14

1) The enzyme has a 3D shape with an active site complementary and specific to the substrate
2) Substrate molecules bind to the active site of an enzyme to form an enzyme-substrate complex’. Reactions occur at the active site and substrate molecules are converted into products
3) The product is released from the active site. The enzyme is chemically unchanged at the end of the reaction and can repeat the reaction many times.

Question 15

What are the 5 characteristics of enzymes?

Answer 15

1) Speed up chemical reactions
2) Specific in action
3) Able to be used over and over again
4) Affected by temperature
5) Affected by pH

Question 16

How do enzymes speed up chemical reactions?

Answer 16

Enzymes speed up chemical reactions by lowering the activation energy required to start the reaction

Question 17

How are enzymes specific in their action?

Answer 17

Enzymes are specific in their action as only substrates with a complementary shape to the active site of the enzyme can bind.

Question 18

Why can enzymes be re used over and over again?

Answer 18

Enzymes remain chemically unchanged a the end of a reaction

Question 19

Describe what happens to enzymes at a low temperature

Answer 19

Enzymes are less active at a low temperature
- Less thermal energy converted to kinetic energy
- Enzymes and substrate molecules move slowly
- Rate of effective collision between substrate molecules and enzyme is very low

Question 20

Describe what happens to enzymes at increasing temperature

Answer 20

Enzymes are increasingly active at an increasing temperature
- More thermal energy converted to kinetic energy
- Enzymes and substrate molecules move faster and faster
- Rate of effective collision between substrate molecules and enzyme increases

Question 21

Describe what happens to enzymes at optimum temperature

Answer 21

Enzymes are most active at optimum temperature
- Most thermal energy converted to kinetic energy
- Enzymes and substrate molecules move fastest
- Rate of effective collision between substrate molecules and enzyme is highest

Question 22

What is the optimum temperature for humans?

Answer 22

37 degrees celcius

Question 23

Describe what happens to enzymes at above optimum temperature

Answer 23

Enzyme reaction rapidly decreases
- High heat causes the breaking of chemical bonds
- Active site of the enzyme molecule loses its original 3D shape
- The active site is no longer complementary to the shape of the substrate molecule
- Enzymes denature

Question 24

How are enzymes affected by pH?

Answer 24

1) If enzymes are placed in pH conditions that vary from optimum, enzymes will denature
2) Extreme changes in acidity/alkalinity causes enzymes to denature

Question 25

What is denaturation?

Answer 25

The change in 3D structure of an enzyme or any other soluble protein caused by heat/chemicals/acids/alkali