Enzymes

Question 1

Describe the Induced fit model

Answer 1

Modification of the lock and key hypothesis

Substrate is not complementary to the active site and when it binds to the active site the site changes shape to become complementary

Forms an enzyme substrate complex

Question 2

What are enzymes and how do they work

Answer 2

Enzymes are biological catalysts that catalyse by lowering activation energy by putting stress on bonds

Question 3

What are factors which affect enzyme-controlled reactions

Answer 3

Temperature
pH
Substrate concentration
Enzyme concentration

Question 4

How does an enzyme function

Answer 4

Dependent on the specific 3D shape of its active site

Question 5

What is the effect of Low temperature on enzymes and why does this happen

Answer 5

Low temperatures either prevent reactions from occurring or slow them down
Molecules move slower leading to a lower frequency of collisions

Question 6

What is the effect of high temperature on enzymes and why does this occur

Answer 6

Molecules move faster meaning a higher frequency of successful collisions between substrate molecules and and enzyme active site

However too high temperatures lead to bonds holding the enzyme to break causing the tertiary structure of the protein to change which permanently damages the active site

The enzyme has denatured

Question 7

What is the optimum temperature

Answer 7

Where enzymes are working at their highest frequency leading to the highest amount of enzyme-substrate complexes to form

Question 8

How does enzyme concentration affect the rate of reaction

Answer 8

The higher the enzyme concentration the greater the number of active sites available and the greater likelihood of an enzyme-substrate complex to form

Only occurs if their is sufficient substrate available and if substrate is limited increasing the enzyme conc has no effect

Question 9

What is the effect of extreme pH

Answer 9

enzyes are denatures

Hydrogen and ionic bonds hold the tertiary structure together

excess of H+ and OH- ions can cause these bonds to break

This denatures the enzymes active site meaning less enzyme-substrate complexes can form and eventually these complexes can no longer form

Question 10

What is an enzyme inhibitor

Answer 10

Substrates than interfere with the functioning of an enzymes active site

Question 11

What are the two types of enzyme inhibitors

Answer 11

competitive and non-competitive

Question 12

How does an competitive enzyme inhibitor work

Answer 12

Active site is occupied by the competitive inhibitor substrate which has a similar structure to actual substrate

This prevents entry of other substrate reducing the amount of enzyme substrate complexes which could form

][

Question 13

How do non-competitive inhibitors work

Answer 13

Inhibitors bind to a site on the enzyme that isn’t the active site which changes the tertiary structure

This leads to change in active site shape making it no longer complementary to the substrate

no enzyme substrate complex can form

Question 14

How can you reverse the effect of non-competitive inhibitos

Answer 14

Increasing the substrate concentration

Question 15

Explain how the active site of an enzyme causes a high rate of reaction

Answer 15

Lowers activation energy and the induced fit ccasues the active site of enzyme to chane shape so enzyme substrate complex causes bonds to break.

Question 16

How does the formation of an enzyme-substrate complex increase the rate of reaction

Answer 16

Reduces activation energy due to stress on bonds

Question 17

Why does the enzyme maltase only catalyse the breakdown of maltose

Answer 17

Active site of enzyme has a specific active site and tertiary structure to the substrate
Only maltose can fit to form an enzyme substrate complex