Factors Affecting Enzyme Activity

Question 1

How can you measure the rate of reaction?

Answer 1

• How fast the product is made.

* How fast the substrate is broken down.

Question 2

What is different between the beginning of a reaction and the end of a reaction?

Answer 2

There are different molecules present at the end of a chemical reaction than there are at the beginning.

Question 3

How can you measure the rate of reaction by how fast the product is made?

Answer 3

By measuring the amount of end product preset at different times during the experiment.

Question 4

How can you produce the end products in a chemical reaction?

Answer 4

Substrate molecules have to be used up.

Question 5

How can you measure the rate of a reaction by how fast the substrate is broken down?

Answer 5

By measuring the amount of substrate molecules left at different times during the experiment.

Question 6

What affects the rate of an enzyme-controlled reaction?

Answer 6

• Temperature
• pH
• Substrate concentration
• Enzyme concentration

Question 7

How does temperature affect the rate of an enzyme-controlled reaction?

Answer 7

•When it is increased the rate of the reaction increases •When it is decreased so does the reaction rate.

Question 8

Why does a higher temperature increase the rate of an enzyme-controlled reaction?

Answer 8

• The substrate molecules are more likely to collide with the enzyme’s active site.
• The collisions are more likely to result in an enzyme-substrate complex.

Question 9

Why are the substrate molecules more likely to collide with enzymes at higher temperatures?

Answer 9

Because more heat means more kinetic energy, so molecules move faster.

Question 10

Why are the enzyme-substrate collisions more likely to result in a complex at higher temperatures?

Answer 10

Because the energy of these collisions increases, so they collide with more force.

Question 11

What happens when the temperature of a reaction gets too high?

Answer 11

The enzymes are denatured and the reaction stops.

Question 12

How do high temperatures denature enzymes?

Answer 12

• The enzyme’s molecules vibrate more.

* The vibrations break some of the hydrogen bonds that hold the enzymes tertiary structure together.

Question 13

What does enzymes being denatured cause the reaction to stop?

Answer 13

It can’t catalyse the reaction anymore.

Question 14

Why can’t denatured enzymes catalyse their reaction anymore?

Answer 14

Because when the enzyme’s tertiary structure is changed, the active site changes shape and is no longer complementary to the substrate.

Question 15

What does the effect of temperature on enzymes look like?

Answer 15

Image

Question 16

Why are low temperatures not optimum for enzyme activity?

Answer 16

Because even tho the enzyme and substrate molecules are complementary, they do not have enough energy to collide.

Question 17

What is the common optimum temperature for enzymes?

Answer 17

Those in humans at 37c

Question 18

What does a graph showing the effect of temperature on the rate of an enzyme-controlled reaction look like?

Answer 18

image

Question 19

What do all enzymes have concerning pH

Answer 19

An optimum pH value.

Question 20

What is the optimum pH value of humans?

Answer 20

7 (neutral)

Question 21

What are some optimum pH value exceptions?

Answer 21

Pepsin works best at pH2 (acidic).

Question 22

Why does pepsin work best at pH2?

Answer 22

Because its function takes place in the stomach.

Question 23

What do enzyme optimum pH values always match?

Answer 23

Their function.

Question 24

Why cant enzymes be in areas of pH values that are different to their optimum pH?

Answer 24

The enzyme becomes denatured, and the active site changes shape.

Question 25

Why do enzymes become denatured at the wrong pH?

Answer 25

Because the H+ and OH- ions found in acids and alkalis can disrupt the ionic and hydrogen bonds that hold the enzyme’s tertiary structure in place.

Question 26

What does a graph showing the effect of pH on the rate of an enzyme-controlled reaction look like?

Answer 26

image

Question 27

How does substrate concentration affect enzyme activity?

Answer 27

• The higher the substrate concentration, the faster the reaction.
• The lower the substrate concentration, the slower the reaction.

Question 28

Why does a higher substrate concentration increase the rate of reaction?

Answer 28

Because more substrate molecules means more enzyme-substrate collisions as more active sites will be occupied.

Question 29

When does increasing substrate concentration stop increasing the rate of an enzyme-controlled reaction?

Answer 29

Until the saturation point.

Question 30

What is the saturation point?

Answer 30

When all enzyme active sites are full, and adding more substrate does not affect the rate of reaction.

Question 31

What does the affect of changing the substrate concentration on the rate of reaction look like?

Answer 31

image

Question 32

What does a graph showing the effect of substrate concentration on the rate of an enzyme-controlled reaction?

Answer 32

image

Question 33

What does changing the enzyme concentration do the rate of reaction?

Answer 33

It increases it (sometimes up to the saturation point like substrate concentration).

Question 34

How does adding more enzyme increase the rate of reaction?

Answer 34

The molecules are more likely to collide and form enzyme-substrate complexes.

Question 35

What happens when you increase the enzyme concentration when the substrate concentration is limited?

Answer 35

There comes a point where all the substrate molecules are in an active site, so adding more enzymes has no further effect.

Question 36

What does a graph showing the effect of enzyme concentration on the rate of an enzyme-controlled reaction look like?

Answer 36

image

Question 37

How can enzyme activity be prevented?

Answer 37

By enzyme inhibitors.

Question 38

What can inhibition be?

Answer 38

• Competitive

* Non-competitive

Question 39

How do competitive inhibitors stop a reaction taking place?

Answer 39

They compete with the substrate molecules to bind to the enzymes active site and block it.

Question 40

How can competitive inhibitors block the enzyme’s active site?

Answer 40

They have a similar shape to the substrate and thus are complementary to the enzyme’s active site.

Question 41

How do competitive inhibitors prevent enzyme activity?

Answer 41

They block the active site so no substrate molecule can fit in, so no reaction takes place.

Question 42

What does competitive inhibition depend on?

Answer 42

The relative concentrations of the substrate and the inhibitor.

Question 43

What happens if substrate concentration is higher than competitive inhibitor concentration?

Answer 43

The substrate’s chances of getting to an active site before an inhibitor increases.

Question 44

What happens if there is a higher concentration of competitive inhibitor than substrate?

Answer 44

The inhibitor will take up nearly all of the active sites and hardly any substrate will react.

Question 45

What does competitive inhibition look like?

Answer 45

image

Question 46

What does a graph showing the effect on a competitive inhibitor on the rate of an enzyme-controlled reaction look like?

Answer 46

image

Question 47

How do non-competitive inhibitors prevent enzyme activity?

Answer 47

They cause the enzyme’s active site to change permanently so substrates can no longer bind.

Question 48

How do non-competitive inhibitors permanently change the enzyme’s active site?

Answer 48

• They bind to the enzyme at the allosteric site (away from the enzyme’s active site).
• This changes the tertiary structure of the active site.

Question 49

What happens when substrate concentration is higher than non-competitive inhibitor concentration?

Answer 49

This has no effect as non-competitive inhibitors don’t compete with substrate molecules to bind to the enzyme’s active site as they are a different shape.

Question 50

Which inhibitor is best at its job?

Answer 50

Non-competitive inhibitors because their inhibition is permanent.

Question 51

What does non-competitive inhibition look like?

Answer 51

image

Question 52

What does a graph showing the effect of a non-competitive inhibitor on the rate of an enzyme-controlled reaction look like?

Answer 52

image