Enzymes

Question 1

What does each enzyme do to the activation energy?

Answer 1

Each enzyme lowers the activation energy of the reaction it catalyses

Question 2

What are the two theories used to describe how enzyme substrate complexes form?

Answer 2

♡ The induced fit model of enzyme actions ♡The lock and key method

Question 3

What is Specificity?

Answer 3

Each enzyme can only combine with one substrate due to their complementary shape so they’re SPECIFIC

Question 4

What is activation energy?

Answer 4

The energy required to kickstart a reaction

Question 5

What is an inhibitor?

Answer 5

Substances which when added to a mixture of enzyme and substrate solutions, reduce the rate of reaction. They do this by combining with enzyme molecules to form enzyme inhibitor complexes

Question 6

What are enzymes?

Answer 6

Globular proteins

Question 7

Describe the structure of enzymes

Answer 7

♡ They have a precise tertiary structure to give them a particular shape ♡The functional part is the active site- a hollow depression on one side of the molecule

Question 8

Where does the substrate bind to the enzyme?

Answer 8

The active site

Question 9

What word describes the shape of the substrate compared with the shape of the active site?

Answer 9

Complementary…shape to the substrate the enzyme works on

Question 10

Why do we need enzymes?

Answer 10

× Our body temp isnt high enough for reactions to occur naturally.
× The activation energy for majority of reactions is too high without an enzyme at the temp at animals exist

Question 11

What is the definition of activation energy?

Answer 11

× The energy put in to get a reaction started
× Energy needed to get a reaction going
× Activation energy is the least amount of energy required to activate atoms or molecules to which they can undergo a reaction

Question 12

What do enzymes do in relationship to activation energy?

Answer 12

Enzymes reduce activation energy

Question 13

How do enzymes reduce activation energy?

Answer 13

Enzymes decrease AE by holding the substrates in such a way that they react more easily (anabolic reactions) or they put a strain on a bond that will more easily break (catabolic reactions)

Question 14

What is a catalyst?

Answer 14

A substance that which changes the rate of a chemical reaction without being changed itself

Question 15

What is an enzyme?

Answer 15

A biological catalyst

Question 16

What is an active site?

Answer 16

The special site in the structure of an enzyme where the substrate binds.

Question 17

What is an enzyme substrate complex?

Answer 17

The enzyme and substrate bind together

Question 18

What factors affect the rate of an enzyme controlled reaction?

Answer 18

× Temperature
× pH
× Concentration of substrate
× Concentration of enzyme

Question 19

How do we express the rate?

Answer 19

The speed that an enzyme works at is expressed as the TURNOVER NUMBER which is the number of substrate molecules which one molecule of enzyme can turn into produced per minute.

Question 20

what is the typical value for a turnover number?

Answer 20

200 000

Question 21

how can the rate be measured?

Answer 21

× Increase in product over time

× Decrease in substrate over time

Question 22

What happens in the course of a reaction?

Answer 22

× initially there is a very high concentration of substrate molecules.
× As substrate is converted into product there are less and less substrate molecules left for the enzyme to act upon and thus the rate decreases
× The initial rate of reaction is always the fastest and this can be calculated by calculating the slope of the tangent as close to zero as possible

Question 23

Explain and describe the the change in rate due to temperature (p1.)

Answer 23

As we increase the temperature from (give figures) the rate of reaction increases
∆ the kinetic energy of the enzyme and the substrate molecules increases
∆ more frequent successful collisions so you gonna form more enzyme substrate complexes produced
∆ faster rate of reaction

Question 24

Explain and describe the the change in rate due to temperature (p2.)

Answer 24

rate of reaction is at its highest. Biggest turnover point. So optimum temperature for the enzyme .
∆ You have more enzyme substrate complexes being formed here than any other point

Question 25

Explain and describe the the change in rate due to temperature (p3.)

Answer 25

between (give figures) we get a gradual decrease in rate of reaction - enzyme is denatured
∆ vibration of enzyme molecule causes H bonding to break
∆ This means the tertiary structure breaks down as the polypeptide chain becomes unravelled
∆ the active site changes shape and substrate molecules will no longer fit
∆ fewer enzyme substrate complexes are formed
∆ The rate of reaction falls

Question 26

How can changing the pH can reduce the rate of reaction?

Answer 26

×changing the pH changes the concentration of H+ ions
× it disrupts the ionic bonding holding the tertiary structure together
× it affects the charges on the R groups that line the active site so temporary bonding with the substrate may no longer occur
× the shape of the active site changes- denatures
× The substrate will no longer fit into the active site
× fewer enzyme substrate complexes are formed
× The rate of reaction is reduced

Question 27

The speed at which an enzyme works is dependent on three factors. Mame then

Answer 27

∆ Temperature
∆ pH
∆ Concentration

Question 28

Describe how temperature affects the speed of an enzyme

Answer 28

Higher temperatures increases the speed at which the parties (both enzyme and substrate) move around. This increases the chances that a successful collision will take place due to collision theory
∆ Increasing temperature speeds up the rate by which enzymes denature so high temperatures will not necessarily lead to a faster reaction

Question 29

Describe how pH affects the speed of an enzyme

Answer 29

The active site if an enzyme is only stable at a specific pH.
Changing the pH leads to the enzyme being less efficient
Drastic changes to pH causes the enzyme to denature permanently

Question 30

Describe how concentration affects the speed of an enzyme

Answer 30

Like any chemical reaction increasing the concentration of the reactants will increase the rate of reaction (how much product is formed in a fixed time)

Question 31

Explain why there will be a low reaction rate if there is little substrate but many enzyme molecules

Answer 31

+ very few enzyme complexes are made

+ most of the active site is unused

Question 32

explain why there will be a fast reaction rate if you increase the substrate concentration

Answer 32

+ more enzyme complexes can be formed so products are released

Question 33

Explain the effect on the rate of reaction if you increase the substrate concentration further

Answer 33

+ the enzyme is saturated

+ maximum turnover rate here

Question 34

As the volume of enzyme is reduced the initial rate of reaction decreases. Why?

Answer 34

There isn’t as much enzyme to make product with

Question 35

Describe the mechanism of action with a COMPETITIVE inhibitor

Answer 35

× Competitive inhibitor has a complementary shape to the active site
× the substrate and inhibitor will compete with each other for the active site
× reduces the rate of reaction because the number of active sites are less available per unit of time

Question 36

Give the use of a competitive inhibitor

Answer 36

antibiotics and some drugs work as competitive inhibitors and destroy bacteria by combining the enzymes that allow bacteria to function - reduces toxic shock

Question 37

Describe the mechanism of action with a NON COMPETITIVE inhibitor

Answer 37

× Joins at a place that’s not the active site, changing the shape of the enzyme so substrate won’t fit
× The enzyme won’t work
×inhibitor binds to the enzyme just not the active site (in a sense its better than the competitive one)
× the bonding is tertiary structure is changed of the enzyme

Question 38

Describe what is happening between the initial rate of reaction and substrate concentration in relation to a competitive inhibitor

Answer 38

A) Both inhibitor and substrate compete for active sites so less enzymes active site is available
× so rate is reduced
× some product being made but lower than before
B) more substrate so inhibitors being out competed so rate increases and more product being made

Question 39

Describe what is happening between the initial rate of reaction and substrate concentration in relation to a non competitive inhibitor

Answer 39

A) the enzyme shape is that shape so that no substrate can fit so the rate of reaction is permanently lowered no matter how much substrate and concentration is used

Question 40

Describe the inhibition without a inhibitor

Answer 40

1) Fewer substrate molecules than enzyme molecules. initial rate of reaction low
2) Approx. equal numbers of substrate and enzyme molecules. Maximum initial rate of reaction
3) Adding excess substrate does not increase initial rate of reaction as all active sites being uses initially

Question 41

Describe the inhibition without a competitive inhibitor

Answer 41

1) inhibitor competes for active site. initial rate of reaction lower than situation where no inhibitor involved
2) Now there are more substrate molecules to compete with the inhibitor. The initial rate of reaction increases but still falls below
3) Now there are many more substrate molecules competing with the inhibitor. The initial rate of reaction almost reaches the maximum achieved with no inhibitor present. The inhibitor now infrequently blocks an active site

Question 42

Describe the inhibition without a non- competitive inhibitor

Answer 42

1) Non competitive inhibitors binds to the enzyme just not the active site. This changes the shape of the active site so now rate of reaction reduced due to less substrates being able to bind with active sites
2) With more substrate molecules all the active sites are full. This is the maximum initial rate of reaction that can be achieved. The non competitive inhibitor is still effectively blocking a percentage of the enzyme molecules .
3) Continuing to increase the substrate concentration has no effect on the initial rate of reaction. The substrate molecules can’t compete with non competitive inhibitor. A percentage of the enzyme molecules are still effectively blocked

Question 43

Explain the structure of enzymes

Answer 43

❤️ Has weak hydrogen bonds that can break under heat

❤️ has a tertiary structure
❤️the tertiary structure can break down as polypeptide chains unravel
❤️so active site changes so substrate will no longer fit
❤️fewer enzyme substrate complexes form

Question 44

Why is an enzyme described as a catalyst?

Answer 44

Because it can can change the rate of reaction without changing itself

Question 45

What are they made from?

Answer 45

Amino acids

Question 46

What is the functional part of the enzyme called?

Answer 46

The active site

Question 47

How is the active site formed?

Answer 47

It has a tertiary structure

Question 48

Why does rate of reaction fall?

Answer 48

ROR falls because the temperature increases causing hydrogen bonds to alter the enzyme tertiary structure
Enzyme denatures
Active site is no longer complementary so enzyme complexes don’t form so less product so rate decreases