Enzymes, inhibitors, pH

Question 1

What are enzymes?

Answer 1

biological catalysts that speed up the rate of metabolic reactions

Question 2

What are enzymes made of?

Answer 2

made up of amino acids

Question 3

What type of structure do enzymes have?

Answer 3

globular proteins with tertiary structure

Question 4

What is the active site?

Answer 4

the part of the molecule where the substrate fits during a reaction

Question 5

How does an active site lose it’s shape?

Answer 5

the bonds that hold the tertiary structure together (hydrogen bonds/disulphide bridges/ionic bonds) are broken so the shape changes

Question 6

What does an enzyme’s 3D shape depend on?

Answer 6

the unique sequence of amino acids in the primary structure

Question 7

What is activation energy?

Answer 7

the minimum amount of energy required for a reaction to take place

Question 8

Why can the activation energy NOT be provided through heating in the body?

Answer 8

because the human body has a temperature of 37C, so enzymes lower the activation energy required

Question 9

What are the two different types of models of enzyme action?

Answer 9

lock and key
induced fit

Question 10

What is the lock and key model?

Answer 10

the active site and the enzyme are exactly complementary- fit together perfectly

Question 11

What is the induced fit model?

Answer 11

the complementary substrate binds to the active site of the enzyme to form an enzyme-substrate complex. as the substrate binds the active site moulds around the substrate- it is not a perfect fit initially

Question 12

What has to happen for enzymes to have an effect?

Answer 12

it has to come into contact with the substrate
it has to have a complementary active site to the substrate

Question 13

What are the four factors impacting enzymes?

Answer 13

temperature
pH
substrate concentration
enzyme concentration

Question 14

How does temperature impact the enzyme?

Answer 14

as temperature increases, so does the rate of enzyme activity (until the temperature surpasses the optimum temperature)

Question 15

Why does the temperature impact the enzyme in this way?

Answer 15

the temperature increase means that the molecules have more kinetic energy, so move around faster, making the substrate more likely to collide with the active sites

Question 16

Why does the enzyme denature after the temperature increases past the optimum temperature?

Answer 16

due to the fact that the molecules are vibrating so much that some of the bonds (like the ionic bonding) break, causing the active site to change shape so the enzyme-substrate complexes can no longer form

Question 17

How does pH impact the enzyme?

Answer 17

each enzyme has it’s own optimum pH, and the enzyme rates are the most efficient at the correct pH

Question 18

Why does the pH impact the enzyme in this way?

Answer 18

if the pH is too high or too low, then the H+ and OH- ions found in acid and alkalis can disrupt the ionic/hydrogen bonds that holds the tertiary structure in place, if this changes shape then enzyme-substrate complexes can no longer form

Question 19

How does substrate concentration impact the enzyme?

Answer 19

as the substrate concentration increases, so does the rate of enzyme activity, up to the saturation point

Question 20

Why does substrate concentration impact the enzyme in this way?

Answer 20

more substrate means more chance of collision between substrate and enzyme

Question 21

What is the saturation point and why does it stop the rate of reaction?

Answer 21

the saturation point is where all of the enzymes’ active sites are filled up by substrate, so no more enzyme-substrate complexes can be formed

Question 22

How does enzyme concentration impact the enzyme?

Answer 22

as the enzyme concentration increases, so does the rate of enzyme activity

Question 23

Why does the rate of enzyme activity slow down/stop despite the increase of enzyme concentration?

Answer 23

because as soon as all of the substrate is used, the amount of enzymes will not increase the rate of reaction anymore as there is no more substrate to form enzyme-substrate complexes

Question 24

Why is the body 37C?

Answer 24

any further increase (due to fever etc) would denature the enzyme

other proteins may be denatured at a higher temperature

additional food/energy required to sustain the body at a higher temperature would be too great

Question 25

What are enzyme inhibitors?

Answer 25

they slow down or stop enzyme reactions

Question 26

What are the two types of enzyme inhibitors?

Answer 26

competitive and non-competitive

Question 27

What is a competitive inhibitor and how does it stop the enzyme?

Answer 27

the competitive inhibitor is a similar shape to the substrate and so is able to ‘compete’ for the active site and hence block the substrate

Question 28

How do we reduce the effect of competitive inhibitors?

Answer 28

by increasing the substrate concentration

Question 29

What happens to the amount of product produced when competitive inhibitors are involved?

Answer 29

all of the product will still be produced but the time it takes to produce it slower

Question 30

What is a non-competitive inhibitor and how does it stop the enzyme?

Answer 30

the non-competitive inhibitor attaches to a site away from the active site and so this alters the shape of the active site, so the substrate is unable to bind and form enzyme-substrate complexes

Question 31

How do we reduce the effect of non-competitive inhibitors?

Answer 31

we cannot reduce the effect of non-competitive inhibitors by increasing the concentration of substrate as they are not competing for the same site

Question 32

What is largely controlled by non-competitive inhibitors?

Answer 32

metabolism

Question 33

How can the non-competitive inhibitors control reactions?

Answer 33

they can temporarily deactivate the enzyme when the product is not needed

Question 34

How do you calculate the pH of a solution?

Answer 34

-log(H+ concentration)

EXAMPLE=
H+ concentration is 3.28x10^-4 = -log(3.28x10^-4)
so the pH is 3.48

Question 35

How do you calculate the H+ ion concentration of a solution?

Answer 35

1x10^(-pH)

EXAMPLE=
pH is 3.6 =
1x10^(-3.6) = 2.51x10^4
so the H+ ion concentration is 2.51x10^4