Year 12 Proteins and enzymes

Question 1

Name the monomer used to make proteins.

Answer 1

Amino acid

Question 2

Name the 2 substances made when 2 amino acids are joined together.

Answer 2

Dipeptide

Water

Question 3

Name the type of reaction used to join 2 amino acids together.

Answer 3

Condensation

Question 4

Name the bond that joins 2 amino acids together.

Answer 4

Peptide

Question 5

How many different amino acids are there and how do they differ?

Answer 5

20

R group is different.

Question 6

Name the molecule made when many amino acids are joined together.

Answer 6

Polypeptide/protein

Question 7

What is the primary structure of a protein/polypeptide?

Answer 7

Specific sequence of amino acids joined by peptide bonds.

Question 8

What is the secondary structure of a protein?

Answer 8

Specific folding of the primary structure held together by hydrogen bonds.

Question 9

What is the tertiary structure of a protein.

Answer 9

Specific folding of the secondary structure held together by hydrogen, ionic or disulfide bridges.

Question 10

What is the quaternary structure of a protein?

Answer 10

Two or more polypeptides joining to make a functional protein.

Question 11

Describe a biochemical test for protein.

Answer 11

Biuret test

Add sodium hydroxide solution and copper sulfate solution.

Positive results - lilac
Negative result - blue

Question 12

Explain the effect of increasing temperature on an enzyme controlled reaction until the optimum temperature is reached.

Answer 12

As temperature increases
The KE of enzyme and substrate increases.
More successful collision between substrate and active site.
More enzyme substrate complexes formed.
Faster rate of reaction.

Question 13

Describe the induced fit model of enzyme action.

Answer 13

Active site and substrate are not complementary.

Active site changes shape to become complementary when an enzyme substrate complex is formed.

Question 14

What is the role of an enzyme?

Answer 14

Catalyses a reaction by reducing the activation energy.

Question 15

Name the structure formed when an enzyme and substrate combine.

Answer 15

Enzyme substrate complex

Question 16

Explain the effect of increasing temperature beyond the optimum temperature for an enzyme.

Answer 16

Enzymes denatures 
Hydrogen bonds break
Tertiary structure of enzyme changes. 
Active site changes shape.
Active site no longer complementary to the substrate.
No enzyme substrate complexes formed. 
Rate of reaction decreases.

Question 17

Explain the effect of changing the pH on the rate of an enzyme controlled reaction.

Answer 17

As the environment becomes too acidic or Enzymes denatures
Hydrogen bonds break
Tertiary structure of enzyme changes.
Active site changes shape.
Active site no longer complementary to the substrate.
No enzyme substrate complexes formed.
Rate of reaction decreases

Question 18

Describe the effect of adding a competitive inhibitor to an enzyme controlled reaction

Answer 18

As concentration of competitive inhibitor increases the rate of reaction decreases

Question 19

Explain how a competitive inhibitor affects the rate of an enzyme controlled reaction.

Answer 19

Competitive inhibitor and substrate have a similar shape.
Competitive inhibitor enters the active site.
Preventing the substrate gaining access to the active site.
Fewer ES complexes formed.
Rate of reaction decreases.

Question 20

Describe the effect of adding a non-competitive inhibitor to an enzyme controlled reaction.

Answer 20

Decreases the rate of the reaction.

Question 21

Explain the effect of adding a non-competitive inhibitor to an enzyme controlled reaction.

Answer 21

Non-competitive inhibitor has a different shape to the substrate.
Non-competitive inhibitor bonds to an allosteric site.
Changes the tertiary structure of the enzymes.
Changes the shape of the active site.
Substrate no longer complementary to active site.
Fewer ES complexes formed
Rate of reaction decreases.

Question 22

Describe the effect of increasing enzyme concentration on the rate of an enzyme controlled reaction.

Answer 22

As enzyme concentration increases the rate of the reaction increases.
The rate then remains constant/plateau/levels off.

Question 23

Explain the effect of increasing enzyme concentration on the rate of an enzyme controlled reaction.

Answer 23

As enzyme concentration increases rate the reaction increases
More successful collisions between enzyme active site and substrate.
More ES complexes formed.

Plateau
Excess enzymes - insufficient substrate available to enter the active sites.

Question 24

Describe the effect of increasing substrate concentration on the rate of an enzyme controlled reaction.

Answer 24

As substrate concentration increases
More successful collisions between enzyme active site and substrate.
More ES complexes formed.

Plateau
Excess substrate available.
All active sites are full at all times.
Rate of reaction cannot increase.

Question 25

Describe how you would work out the rate of an enzyme controlled reaction at 10s from a graph showing time on x axis and amount of product made on y axis

Answer 25

Draw tangent to line of best fit.
Read off graph
Change in time
Change in amount of product made

Amount of product/Time