FACTORS AFFECTING ENZYME ACTION

Question 1

What 2 things have to occur for an enzyme to work

Answer 1

1) come into physical contact with its substrate

2) have an active site that fits the substrate

Question 2

What do we usually measure to see the progress of an enzyme-catalysed reaction

Answer 2

its time-course

Question 3

What is a reactions time-course

Answer 3

how long it takes for a particular event to run its course

Question 4

What are the 2 time-course changes are measured most frequently

Answer 4

1) formation of the products of the reaction

2) the disappearance of a substance

Question 5

Explain the shape of the graph of enyme: substrate (as substrate decreases so does the amount of product formed, decreasing rate) using

Answer 5

1) at first=lots of substrate and no product
2) lots of substrate & lots of empty active sites
3) all substrates filled and substrate rapidly broken into product
4) as substrate breaks down = less substrate and more product
5) becomes more difficult for substrate to find empty active site (less substrate, more active site filled) so disappearance of substrate decreases & formation of product also decreases
6) at the end = no substrate left, so no product made

Question 6

How do you find the rate of change of a graph

Answer 6

measuring the gradient at that point

Question 7

How do you measure the gradient at that point

Answer 7

draw a tangent

Question 8

What are the 5 factors that affect enzyme action

Answer 8

1) temperature
2) pH
3) enzyme concentration
4) substrate concentration
5) enzyme inhibition

Question 9

In what way does temperature affect enzyme action

Answer 9

higher temperature = rate of reaction increases

Question 10

Which 2 ways does temperature have this affect

Answer 10

1) Higher temperature = higher kinetic energy of molecules, meaning the molecules move around faster and are more likely to collide with each more often (enzyme & substrate).
2) Higher temperature = higher energy in collisions, so more likely to lead to a successful collision and therefore a reaction

Question 11

What does temperature increase look like on a graph

Answer 11

rising curve up to a point

Question 12

Draw a graph of the effect of a rise in temperature

Answer 12

rising curve (up to a point)

Question 13

What happens if the temperature becomes too high

Answer 13

the enzyme action slows down as some hydrogen bonds are broken, far too high = denature

Question 14

Why do enzymes denature

Answer 14

the heat breaks the hydrogen bonds in the tertiary structure of the enzyme meaning that the active site changes shape so the substrate no longer fits

Question 15

Can denaturation be un-done

Answer 15

no

Question 16

What is the optimum temperature

Answer 16

temperature that enzymes work best at

Question 17

What is the optimum temperature for human enzymes

Answer 17

40 degrees C

Question 18

Is the optimum temperature the same for all enzymes

Answer 18

no

Question 19

For what 3 reasons might the human body be colder than the optimum temp for enzymes

Answer 19

1) more food would be required that would cancel out the benefits of higher metabolic rate
2) other proteins may be denatured at higher temperatures
3) an increased temperature during things such as illness might mean the enzymes are denatured

Question 20

Why do birds have a higher body temperature than humans

Answer 20

they require more energy from metabolic reactions for flight

Question 21

How does pH effect enzymes

Answer 21

at optimum pH = highest rate of enzyme-controlled reactions, extreme higher/ lower = enzymes denatured

Question 22

What is the pH of a solution

Answer 22

a measure of its hydrogen ion content

Question 23

How do you calculate pH

Answer 23

-log10(H+)

Question 24

Which 2 ways does pH alter enzyme action

Answer 24

1) changes the charges on the amino acids that make up the active site, so the substrate can no longer become attached to the active site
2) the H+ and OH- ions in acid & alkalis can break the ionic and hydrogen bonds that maintains the enzymes tertiary structure

Question 25

Is it common for pH changes to denature enzymes and why

Answer 25

no, because the fluctuations inside organisms are usually small

Question 26

What is the effect of enzyme concentration on the rate of reaction ( with limited amount of substrate throughout)

Answer 26

1) low enzyme con = too few active sites for substrate to bind so some wasted & less likely to collide = slower rate of reaction
2) intermediate enzyme conc = all substrate molecule can occupy active site & more likely to collide = higher rate of reaction
3) high enzyme conc = no further affect as all substrates have binded to active site

Question 27

When does the higher the concentration of enzyme always mean a higher rate of reaction

Answer 27

when the substrate concentration is not limited

Question 28

What does the graph of enzyme conc:rate of reaction look like (limited/ unlimited)

Answer 28

limited = straight line that levels off
un-limited = straight line

Question 29

What is the effect of substrate concentration on the rate of reaction (with limited conc. of enzyme)

Answer 29

1) low substrate conc = too few substrate to occupy all available active sites = rate is only half maximum possibility
2) intermediate substrate conc = all active sites occupied and more likely to collide = rate of reaction higher
3) high substrate conc = no effect, all active sites filled so active sites are ‘saturated’

Question 30

When is the highest rate of reaction of enzymes : substrate and why

Answer 30

initial rate (at the start) , because substrate is used up over time so rate decreases

Question 31

What are heat-loving bacteria

Answer 31

thermophilic

Question 32

What are thermophilic bacteria

Answer 32

heat-loving

Question 33

What are enzyme inhibitors

Answer 33

substances that directly/indirectly interfere with the functioning of the active site of an enzyme

Question 34

What do enzyme inhibitors do

Answer 34

decrease the enzyme activity

Question 35

How many types of enzyme inhibitors are there

Answer 35

2

Question 36

What are the types of enzyme inhibitors

Answer 36

1) competitive

2) non-competitive

Question 37

What are competitive inhibitors

Answer 37

molecules that have a similar shape to the substrate molecule

Question 38

What does the shape of the competitive inhibitor allow them to do

Answer 38

bind to the active site

Question 39

What do competitive inhibitors compete with

Answer 39

the substrate

Question 40

What do competitive inhibitors bind with

Answer 40

the active site

Question 41

What determines the effect of competitive inhibitors effectiveness and how

Answer 41

the concentration of substrate
higher conc of substrate = effect of inhibitor reduced
lower conc of substrate = effect of inhibitor increased

Question 42

Does the competitive inhibitor stay binded to the active site or does it leave, and what does this mean (refer to conc)

Answer 42

It leaves, meaning another molecule takes its place (high conc of substrate = more likely to be substrate)

Question 43

What is an example of a competitive inhibitor

Answer 43

respiratory enzyme that acts on succinate (substrate) - malonate (inhibitor) can inhibit the enzyme by binding to its active site because it has a similar shape to succinate

Question 44

What is a non- competitive inhibitor

Answer 44

molecule with a different shape to the substrate

Question 45

What does a non-competitive inhibitor do

Answer 45

attach themselves to the enzyme at a binding site (NOT active site) that causes the shape of the active site to change = substrate can no longer fit to form an enzyme-substrate complex

Question 46

Does increasing the substrate concentration effect the rate of reaction when a non-competitive inhibitor is present, & why

Answer 46

no, because they are not competing for the active site

Question 47

What is a metabolic pathway

Answer 47

series of reactions in which each step is catalysed by an enzyme

Question 48

What feedbacks can metabolic pathways have

Answer 48

negative & positive

Question 49

What do feedbacks in metabolic pathways result in & what is it known as

Answer 49

the concentration of any chemical being maintained realtively constant, known as end-product inhibition

Question 50

What type of inhibition is end-product inhibition usually

Answer 50

non-competitive