Enzymes

Question 1

What type of protein are enzymes?

Answer 1

Globular

Question 2

What are enzymes?

Answer 2

Biological Catalysts that increase the rate of a chemical reaction without undergoing permanent change or being used up

Question 3

Why can enzymes be effective in small amounts?

Answer 3

They can be reused repeatedly

Question 4

How do enzymes speed up reactions?

Answer 4

They lower the activation energy

Question 5

What 3 things must a reaction have in order to take place naturally?

Answer 5

1) molecules must collide with sufficient energy to alter the arrangement of their atoms
2) the energies of the reactants/products must be in accordance to if its exo- or endothermic
3) must have achieved its activation energy

Question 6

What is the activation energy?

Answer 6

The minimum amount of energy needed to activate the reaction

Question 7

Why can metabolic processes occur rapidly at the human body temperature of 37*C (relatively low)?

Answer 7

Enzymes allow reactions to take place at lower temperatures by lowering the activation energy

Question 8

How would our metabolic reactions occur if we didn’t have enzymes?

Answer 8

Too slowly to sustain life

Question 9

What is the enzyme’s specific 3D shape a result of?

Answer 9

Their sequence of amino acids (primary protein structure)

Question 10

What is the functional specific region on the enzyme?

Answer 10

The active site

Question 11

What is the active site made up of?

Answer 11

A relatively small number of amino acids.

Question 12

What does the active site form within the enzyme?

Answer 12

A small depression (dip)

Question 13

What is the molecule which the enzyme acts on?

Answer 13

The substrate

Question 14

What is formed when the molecule fits into the depression?

Answer 14

An enzyme-substrate complex

Question 15

How is the substrate held within the active site?

Answer 15

By bonds that temporarily form between certain amino acids of the active site and groups on the substrate molecule

Question 16

Do amino acids that do not form part of the active site change its shape? (And therefore effect it’s function)

Answer 16

Yes - may be one that forms hydrogen bonds with other amino acids, so tertiary structure may be changed - including the active site - so that the substrate may no longer fit.

Question 17

What is the current model for the function of enzymes?

Answer 17

The induced fit model

Question 18

What does the “induced fit” model propose?

Answer 18

The active site forms as the enzyme and substrate interact

Question 19

How does the proximity of the substrate effect enzyme that forms the functional active site?

Answer 19

It leads to a change in the enzyme that forms the active site.

Question 20

Why can the enzyme mould itself around the substrate?

Answer 20

It is flexible

Question 21

How does the strain that is put on the substrate molecule by the enzyme as it’s active site changes shape affect the molecule?

Answer 21

Distorts bonds in the substrate and so lowers the activation energy needed to break the bond.

Question 22

Is any change in the enzymes environment likely to change its shape?

Answer 22

Yes

Question 23

What is the previous model for enzymes?

Answer 23

“Lock and key” model - substrate fits exactly the active site of the enzyme

Question 24

What is the main limitation of the lock and key model?

Answer 24

It considered the enzyme to be a rigid structure but it’s structure is flexible

Question 25

What happens if an amino acid within the active site is changed?

Answer 25

The changed amino acid may no longer bind to the substrate, which will then not be positioned correctly - or at all - in the active site

Question 26

What two things must happen with an enzyme to ensure it works?

Answer 26

1) must have an active site which fits the substrate 2) must come into physical contact with the substrate

Question 27

What 3 things affect the rate of enzyme action?

Answer 27

1) pH 2) temperature 3) enzyme concentration

Question 28

What does a rise in temperature increase in the molecules?

Answer 28

The kinetic energy

Question 29

How does an increase in temperature affect the rate of enzyme action?

Answer 29

It increases it - molecules move around more rapidly and collide more often so the enzymes and substrates come together more often so have more effective collisions so more enzyme-substrate complexes are formed in a given amount of time

Question 30

What does a large rise in temperature cause within the enzyme?

Answer 30

Causes the hydrogen and other bonds to break resulting in the enzyme’s active site changing shape

Question 31

What is denaturing?

Answer 31

A permanent change that means the enzyme cannot functions again

Question 32

What is the interval in humans from when enzymes begin to denature and are no longer functional?

Answer 32

45*C - 60*C

Question 33

What are 3 advantages to having our body temperature at 37 degrees ( not 40 degrees - optimum )?

Answer 33

1) additional energy would be needed to maintain the energy - by food 2) at higher temps other proteins apart from enzymes would be denatured 3) at higher temps any further rise in temperature E.G fever would denature the enzymes

Question 34

Why do different animals have difference normal body temperatures?

Answer 34

They have different metabolic rates depending on their lifestyles (E.G birds with flying )

Question 35

What is the pH of a solution?

Answer 35

A measure of its hydrogen ion concentration

Question 36

What is an optimum pH?

Answer 36

The pH at which an enzyme works fastest

Question 37

What happens if the pH is increased or decreased around the optimum?

Answer 37

Rate of enzyme action is decreased

Question 38

What happens if the change in pH is extreme beyond the optimum?

Answer 38

The enzyme becomes denatured

Question 39

What pH would a solution with hydrogen ion concentration 1 x10^-9 have?

Answer 39

pH 9

Question 40

In terms of amino acids, how does a change in pH affect enzymes?

Answer 40

Alters the chargers on the amino acids that make up an active site of an enzyme

Question 41

What happens if the charge on an amino acid within the active site is altered?

Answer 41

The substrate can no longer become attached to the active site and so the enzyme-substrate complex can’t be formed

Question 42

How does a change in pH affect an enzyme in terms of its tertiary structure?

Answer 42

May cause the bonds maintaining the tertiary structure to break, therefore changing the active site’s shape

Question 43

How does the change in H+ ions result in a change in active site ?

Answer 43

Affects the hydrogen and ionic bonds between -NH2 and -COOH groups of the polypeptides that determines the arrangement of the active site

Question 44

Why are enzyme’s activity mostly reduced instead of denatured inside organisms?

Answer 44

pH fluctuations are usually small

Question 45

What happens if there is an increase in enzyme concentration?

Answer 45

- as long as there is an excess of substrate - there is a proportional increase in rate of reaction

Question 46

In what case does increasing enzyme concentration have no effect?

Answer 46

If there is not sufficient substrate to supply all the enzymes active sites at one time - limiting

Question 47

Why does the graph level off?

Answer 47

All the active sites are occupied and the available substrate is already being used

Question 48

Why is there a lower rate of reaction when there is a lower concentration of substrate?

Answer 48

The enzymes have only a limited number of substrate molecules to collide with so the active sites are not working at full capacity.

Question 49

Why does the rate of reaction increase when substrate concentration increases m?

Answer 49

Active sites are filled to the point where all of them are working as fast as they can