5.2 properties of enzymes

Question 1

all enzymes are _________

Answer 1

protein

Question 2

enzymes are made denatured by ___________

Answer 2

high temperature (<40°C)

Question 3

why are enzymes made denatured by high temperature?

Answer 3

protein molecules are damaged by heat

Question 4

enzymes work best at what temperature?

Answer 4

about 37°C (human body temperature)

Question 5

what are the four variables in enzyme activity?

Answer 5

temperature; pH; enzyme concentration; substrate concentration

Question 6

what are the effects of low temperature on enzyme activity?

Answer 6

low temperature = low kinetic energy possessed by the substrate and the enzyme molecules
low kinetic energy > low collisions > low rate of reaction > reduced enzyme activity > enzyme is inactive

Question 7

what is optimum temperature?

Answer 7

the temperature at which an enzyme works the fastest in

Question 8

what causes the active site to change its shape?

Answer 8

when the temperature goes beyond the optimum temperature

Question 9

what would an enzyme be deemed as when its active site changes shape?

Answer 9

the enzyme is said to be denatured

the substrate can no longer bind to the active site of the enzyme

Question 10

denaturation is a _____ process

Answer 10

permanent

Question 11

inactive enzymes can regain ___________ when temperature increases

Answer 11

catalytic function

Question 12

when an enzyme is denatured, its catalytic function is lost _________

Answer 12

permanently

Question 13

most enzymes are in their correct shape at a pH of ___

Answer 13

7

Question 14

what happens to the enzyme if the pH is too acidic or alkaline?

Answer 14

enzyme is denatured; cannot catalyse its reaction

Question 15

rate of enzyme activity is ______ to enzyme concentration

Answer 15

proportional

Question 16

concentration of substrate must be in ______

Answer 16

excess

Question 17

describe the steep line of a graph

Answer 17

• rate of reaction is proportional to the substrate concentration
• enzyme activity increases with substrate concentration as there are still available active sites on enzyme molecules

Question 18

describe the long neutral line of a graph

Answer 18

• rate of reaction is no longer influenced by substrate concentration

Question 19

describe the long neutral line of a graph

Answer 19

• rate of reaction is no longer influenced by substrate concentration
• all the available active sites on enzymes are saturated with substrate molecules
• additional substrate molecules need to compete with each other to bind to the active sites of enzymes
• at this point reaction happens at a constant rate
  (enzyme concentration is constant)

Question 20

characteristics of enzymes

Answer 20

• made of proteins
• not changed by reaction
• can be reused
• only small amount is needed
• specific
• sensitive towards temperature and pH
• can be inhibited (eg mercury, plumbum)
• cofactors are sometimes needed (eg magnesium, vitamin B, vitamin K)