Chap 4: Enzymes

Question 1

Define catalysts

Answer 1

speeds up chemical reactions without being chemically changed at the end

Question 2

What are enzymes?

Answer 2

Biological catalysts which are proteins found in living organisms. It is chemically unchanged after reaction

Question 3

What is activation energy?

Answer 3

Energy needed to start chemical reactions

Question 4

What are enzymes and what do they do?

Answer 4

1. Enzymes are biological catalysts
2. Lower activation energy (which speeds up chemical reactions)
3. Build up or break down complex substances

Question 5

Properties of enzymes

Answer 5

1. Soluble in water
2. Small - enough to diffuse through cell membrane

Question 6

What are digestive enzymes?

Answer 6

enzymes involved in digestion

Question 7

Examples of digestive enzymes

Answer 7

amylase, maltase, protease, lipase

Question 8

What are the two enzyme reactions?

Answer 8

build up or break down complex substances

Question 9

Examples of build up of complex substances

Answer 9

• amino acids use enzymes to build up into polypeptides then lastly proteins
• use for photosynthesis

Question 10

Examples of break down of complex substances

Answer 10

• large food molecules broken down by digestive enzymes
• hydrogen peroxide broken down to oxygen and water

Question 11

What do enzymes catalyse in chemical reaction?

Answer 11

all chemical reactions that occur in organisms (enzymes are only produced when needed)

Question 12

What are enzymes classified?

Answer 12

Based on chemical reactions they catalyse (eg carbohydrases, protease, lipase)

Question 13

Define substrate

Answer 13

substance which enzyme acts on

Question 14

What are active sites?

Answer 14

grooves/pockets on enzyme surface where substrates with matching shapes can fit

Question 15

What is lock and key hypothesis

Answer 15

Lock: Enzyme
Key: Substrate

Question 16

Process of enzyme substrate reaction

Answer 16

1. substrate binds to enzyme of complementary shape
2. results in enzyme-substrate complex
3. enzyme catalyses chemical reaction
4. products are formed
5. products leave enzyme active site
6. enzymes remain chemically unchanged and are free to bind to another substrate

Question 17

Enzyme characteristics?

Answer 17

1. Speeds up chemical reaction [by lowering activation energy]
2. Enzymes are substrate specific
3. Enzymes are required in minimum amounts
4. Enzymes are unchanged after reactions (can be reused)

Question 18

If there is low temperature, what happens to enzymes?

Answer 18

Low temperature
- less energy
- less kinetic energy
- lower rates of collision
- enzymes are less active

Question 19

As the temperature increases (under optimal temperature) what happens to enzymes?

Answer 19

Increasing temperature
- increasing energy
- increasing KE
- increase collisions
- increases enzyme-substrate complex formation rate

Question 20

What is optimum temperature?

Answer 20

When the enzymes are most active [40-45 degree Celsius]

Question 21

What happens when temperature increases after optimal temperature for enzymes?

Answer 21

increasing temperature after optimal temperature
- rapid decrease of enzyme reaction
- enzymes lose original shape
- no longer complementary

Question 22

What happens to enzymes in extremely high temperatures?

Answer 22

Enzymes are completely denatured

Question 23

Define denatured

Answer 23

change in 3D structure of enzymes, caused by change in heat or pH
enzymes no longer acts like catalyst

Question 24

What does a graph of enzyme affect by temperature look like?

Answer 24

unsymmetrical

Question 25

What happens to enzymes at optimal pH?

Answer 25

enzyme activity is highest

Question 26

What happens to enzymes in extremely low or high pH?

Answer 26

enzyme becomes denatured

Question 27

Is optimal pH same for all enzymes?

Answer 27

No. Eg protease have different pH when is stomach vs small intestine