2.1 Enzymes

Question 1

definition of enzymes

Answer 1

proteins that are catalysts and speed up chemical reactions

Question 2

metabolism

Answer 2

is the overall chemical activity of cells

Question 3

substrate

Answer 3

the molecule on which an enzyme acts.

Question 4

denaturation

Answer 4

an irreversible change in protein structure.

Question 5

what is a catalyst?

Answer 5

speeds up (catalyses) chemical reactions that would otherwise take place, but much more slowly.

Question 6

8 things about enzymes

Answer 6

1) are proteins
2) are substrate specific
3) can be reused over and over again
4) are needed in small amounts and are neither reactants or products
5) reduse activation energy required (make a reaction take place more easily)
6) can catalyse a reaction in either direction (most chemical reactions are reversible)
7) do not change the direction of a reactant
8) do not change the final amount of product

Question 7

describe the active site and its role.

Answer 7

The active site is a particular position/specific site on an enzyme which attaches to a specific substrate.

Question 8

what are enzymes

Answer 8

• enzymes increase the rate of chemical reactions which would otherwise occur too slowly to sustain life • enzymes lower the activation energy required for a reaction to proceed.

Question 9

two processes of enzyme activity

Answer 9

1) LOCK AND KEY - substrate molecules have the right shape to fit an enzyme
2) INDUCED FIT - actual interactions between substrate and enzyme changes the shape of the enzyme to produce the right fit.

Question 10

activation energy

Answer 10

energy required to start a chemical reaction

Question 11

what do chemical reactions involve?

Answer 11

breaking and remaking chemical bonds.

the molecules require a certain amount of activation energy to get the reaction started

Question 12

two factors that affect chemical reactions

Answer 12

1) amount of substrate or enzyme present
2) whether there is an accumulation of product.

however given an unlimited time, the final amount of product in not affected by the amount of enzymes present

Question 13

6 factors which affect enzymes

Answer 13

1) Temperature
2) pH
3) Regulating enzyme affinity
- chemical inhibition
- amounts of reactants
- coenzymes and co factors

Question 14

Temperature

Answer 14

• warming increases the rate of most chemical reactions, including enzyme catalysed reactions
• warm = molecules moving faster more substrate and enzyme interactions
• cooler = molecules moving at a slower pace, less particle interactions
• hot = denaturisation

Question 15

what is denaturation?

Answer 15

• irreversible change in the protein structure
• boiling denatures most enzymes, which is why some vegetables are blanched in boiling water before freezing.
• the boiling water deactivates enzymes which would otherwise cause the vegetables to deteriorate during storage.

Question 16

optimum temperature

Answer 16

range in which the temperature at which the enzymes catalytic activity is the greatest.

• range immediately below the critical temp
• optimal temp for particular enzymes may vary in different species and are related to the normal body temp of enzymes.

Question 17

critical temperature

Answer 17

range at which denaturation of enzymes begin to occur

Question 18

how does pH affect enzymes

Answer 18

• three dimensional structure of proteins is affected by pH

- altering the pH may change the shape of the binding ( active site) and so alter the ‘fit’ between enzyme and substrate

Question 19

what is optimal pH

Answer 19

that at which the fit is best and so the enzyme activity is the greatest

• for many enzymes this is a neutral or sightly acidic pH.

Question 20

what is affinity?

Answer 20

is the ease at which an enzyme binds with its substrate

Question 21

how do cells regulate enzyme affinity and what is it?

Answer 21

• cells can regulate the affinity by of certain key enzymes for their substrate molecules
• they do this by attracting other molecules to the enzyme to alter the shape of its active site.

this allows to increase or decrease the rate of a reaction in particular circumstances

Question 22

chemical inhibition

Answer 22

other chemical substances can inhibit enzyme function by binding to the active site of the enzymes, or by combining with another part of an enzyme in such a way that the shape of the binding site is altered

Question 23

How does the amount of reactant affect the enzyme

Answer 23

rate of a reaction is also affected by the relative amounts of substrate or enzyme present and how much product has accumulated

• if there is more substrate present = net reaction will go to the right
• if product accumulates = the net reaction will slow and eventually begin to go to the left

Question 24

Coenzymes and Cofactors

Answer 24

• coenzymes are very small organic molecules - less complex than proteins - that are associated with particular enzymes and are essential for their activity.

Question 25

what does metabolism involve

Answer 25

it includes the manufacture ( synthesis) of organic molecules, various energy transformation and recycling processes, and the breakdown of unwanted substances