4.2 - Factors Affecting Enzyme Activity

Question 1

How can factors affecting enzyme activity be investigated

Answer 1

Measuring rate of reactions they catalyse

Question 2

Effect of temperature

Answer 2

Increasing temperature increases kinetic energy of particles.
As temp increases, particles move faster and collide more frequently
In enzyme controlled reaction, increase in temperature will result in more successful collisions = increase rate of reaction

Question 3

Temperature coefficient

Answer 3

Q10. Measure of how much rate of reaction increases with a 10C rise in temp. Usually taken as 2 for enzymes (reaction doubles with 10C rise)

Question 4

Denaturation from temperature

Answer 4

Enzymes are proteins.
Structure is affected by temperature.
At higher temperatures, bonds holding protein together vibrate more.
As temp increases, so do vibrations until bond strains and breaks.
Bond breakage causes tertiary structure of enzyme to change shape until it’s been denatured.

Question 5

What happens when enzyme is denatured

Answer 5

Active site changes shape and is no longer complementary to substrate. Substrate no longer fits into active site and enzyme ceases to act as catalyst.

Question 6

Optimum temperature

Answer 6

Temperature at which enzyme has highest rate of activity

Question 7

Optimum temperature for many enzymes in human body

Answer 7

40*C

Question 8

Optimum temperature for many thermophilic bacteria

Answer 8

70*C

Question 9

Optimum temperature for enzymes in psychrophilic enzymes

Answer 9

Below 5*C

Question 10

Difference between temperature being too high or too low

Answer 10

High - decrease is rapid denatured as active site has changed
Low - decrease less rapid as enzyme is just less active

Question 11

Extremely cold environments

Answer 11

Deep oceans
High altitudes
Polar regions

Question 12

Features if enzymes adapted to the cold

Answer 12

More flexible structures so are less stable than enzymes that work at higher temperatures
Smaller temperature changes denature them

Question 13

What is a thermophile

Answer 13

Organism adapted to very hot environments

Question 14

Examples of hot environments

Answer 14

Hot springs

Deep sea hydrothermal vents

Question 15

Features of thermophilic enzymes

Answer 15

More stable due to increased number of bonds particularly H bonds and sulcus bridges in tertiary structures
Shape of enzymes and active sites are more resistant to temperature rises

Question 16

What is a change in pH

Answer 16

Change in H ion concentration

Question 17

Why is pH important

Answer 17

Active site will only be correct shape when in certain H ion concentration

Question 18

How are proteins held in their precise 3D shape

Answer 18

H bonds & ionic binds betwieeen amino acid R groups. Bonds result from interactions between the polar and and charged R groups present on amino acids forming the primary structure

Question 19

What happens when pH changes from optimum

Answer 19

Structure of enzyme and active site site is altered.

If pH returns then protein returns to normal shape and catalyse reaction - renaturation

Question 20

How does H ion concentration affect enzymes

Answer 20

H ions interact with polar and charged R groups
Changing concentration changes degree of interaction
Interactions affect how R groups interact

Question 21

Effect of more H ions

Answer 21

Less R groups can interact

Bonds break and shape of enzyme changes

Question 22

Why does enzyme only function in narrow pH range

Answer 22

Shape of enzyme changes as pH changes

Question 23

Enzyme and substrate concentration

Answer 23

Increased number of either increases rate of collision of active site and substrate
Increases number for enzyme substrate complex
RoR can reach Vmax

Question 24

What happens at Vmax

Answer 24

All active sites are occupied. RoR can only be increased by increasing enzymes or temperature