4 Enzymes

Question 1

What is an enzyme?

Answer 1

A biological catalyst
Made of protein
Lowers activation energy
The active site is complementary to the substrate

Question 2

How do you test for enzymes in a sample?

Answer 2

(Test for proteins)
Biuret’s solution

Question 3

Intracellular vs extracellular

Answer 3

Intracellular: inside cell e.g. catalase
Extracellular: outside cell e.g. amylase

Question 4

Define a catabolic reaction.

Answer 4

Break down

Question 5

Define anabolic reaction.

Answer 5

Build up

Question 6

State if the following are intracellular or extracellular enzymes:
a) catalase
b) trypsin
c) amylase

Answer 6

a) intracellular
b) extracellular
c) extracellular

Question 7

State what the following enzymes catalyse the break down of and the products formed:
a) catalase
b) trypsin
c) amylase

Answer 7

a) hydrogen peroxide into water and oxygen
b) proteins into amino acids (hydrolysis of peptide bonds)
c) starch into maltose (hydrolysis)

Question 8

Explain the lock and key hypothesis.

Answer 8

Substrate enters active site
Enzyme-substrate complex formed
Substrate broken down
Enzyme-products comped formed
Products leave active site

Question 9

Explain the induced fit hypothesis.

Answer 9

Substrate enters active site
Enzymes-substrate complex is formed
Active sight slightly changes shape as substrate binds
Substrate is complementary to active site
Products leave the active site of enzyme

Question 10

Explain one difference between the induced fit hypothesis and the lock and key hypothesis.

Answer 10

Lock and key hypothesis- the enzymes is rigid and the active site does not change shape
Induced fit hypothesis- the active site changes shape slightly as the substrate binds

Question 11

How do enzymes lower activation energy?

Answer 11

When the substrate binds and forms an enzyme-substrate complex it strains the substrate
This distorts the bonds
And lowers the activation energy

Question 12

What does it mean if an enzymes denatures?

Answer 12

The shape of the active site has changed
The enzyme-substrate complex cannot form
The enzyme no longer functions

Question 13

Name 5 factors that have an effect on enzyme activity.

Answer 13

Temperature
pH
Concentration of substrate
Concentration of enzyme
Inhibitors

Question 14

Name 3 ways enzyme catalytic reactions can be measured.

Answer 14

Measure the:
Disappearance of products
Formation of products
Rate of reaction

Question 15

Describe how enzyme activity is affected as temperature increases/ at different pH’s.

Answer 15

Initially, the rate of reaction increases rapidly until it reaches a peak (easy enzyme-substrate contact).
After this, the rate of reaction decreases rapidly until it is finished.
Peak= optimum temperature/pH

Question 16

Explain the term biological catalyst.

Answer 16

A substance that increases the rate of reaction
By lowering the activation energy
It speeds up metabolic reactions

Question 17

Describe how substrate and enzyme concentration affects rate of reaction/ enzyme activity.

Answer 17

As long as the enzyme/substrate concentration is high enough, the relationship between the enzyme/substrate concentration and rate of reaction is linear.
If the enzyme/substrate concentration is not high enough then Vmax is reached (maximum rate of reaction).

Question 18

What is the equation for the temperature coefficient?

Answer 18

Q10= rate at (t + 10 degrees)/ rate at t degrees

Question 19

What bonds are affected when an enzyme denatures and which structure are these bonds in?

Answer 19

Hydrogen and ionic bonds
Tertiary structure

Question 20

Is a denatured enzyme due to
a) temperature
b) pan
always permanent? Explain your answer.

Answer 20

a) yes- the specific shape of the active site is lost
b) no- if the structure is not changed significantly, renaturation can occur (original shape of active site is returned)

Question 21

Explain how low temperature affects enzymes.

Answer 21

The number of successful collisions decreases
Because the molecules have less kinetic energy
Therefore, fewer complexes are formed
And the rate of reaction is slower

Question 22

Explain how increasing the temperature affects enzymes.

Answer 22

The number of successful collisions increases
Because the molecules have more kinetic energy
More substrate-complexes are formed (and more products are formed)
And rate of reaction is faster

Question 23

Define the term ‘inhibitor’ in relation to enzymes.

Answer 23

A substance that indirectly or directly interferes with the functioning of the active site of an enzyme.
Most are temporary attachments, but there are also permanent inhibitors.

Question 24

Describe the differences between competitive and non-competitive inhibitors.

Answer 24

Competitive (C): similar shape to substrate
Non-competitive (N): doesn’t have to be like the substrate
C: can fit into active site of enzyme
N: attached to inhibitor site
C: competes with substrate
N: does not compete with substrate
C: causes a shower reaction
N: causes a change in shape of the active site so the enzyme cannot bind
C: direct
N: indirect

Question 25

What is end product inhibition?

Answer 25

The end product of a chain of reactions inhibits the enzyme in an earlier reaction (in the chain).

Question 26

What is a cofactor?

Answer 26

A non-protein substance
That binds to an enzyme
And is needed for the enzyme to function

Question 27

What is a coenzyme?

Answer 27

An organic cofactor (has carbon)

Question 28

What is a prosthetic group?

Answer 28

A cofactor
That is permanently attached to an enzyme.

Question 29

How do inorganic cofactors work?

Answer 29

They are (often) carriers- they move chemical groups from one enzyme to another
They are changed by participating in a reaction.

Question 30

What is precursor activation?

Answer 30

When an enzyme is activated by something to work.

Question 31

How do inorganic cofactors work?

Answer 31

They help the enzyme and substrate bind (change the shape of the active site to make fit better).
They are not part of the reaction.

Question 32

What is the cofactor for amylase?

Answer 32

Chlorine ion (Cl-)

Question 33

What enzyme is a zinc ion a prosthetic group for?

Answer 33

Carbonic anhydrase

Question 34

Name a source of coenzymes.

Answer 34

Vitamins