enzymes

Question 1

What is the role of enzymes

Answer 1

Biological catalysts

Question 2

What is the role of catalase

Answer 2

Catalase is an intracellular enzyme. Catalase binds to the toxic chemical hydrogen peroxide and turns it into water + oxygen

Question 3

What is the role of amylase

Answer 3

Amylase is produced in the pancreas and released into the small intestine. Turn starch into maltose.

Extracellular enzyme

Question 4

What is the role of trypsin

Answer 4

Produced by the pancreas and released into the digestive system. Breaks down protein molecules into peptides.

Extracellular enzyme

Question 5

Name 3 features of globular proteins

Answer 5

Hydrophilic amino acids
Hydrophobic amino acids buried in their centre
Soluble in water

Question 6

How do enzymes increase the RoR?

Answer 6

Enzymes provide a pathway for the reaction with a lower energy barrier.

Question 7

What is the lock and key model?

Answer 7

Scientists thought the tertiary structure of the active site was fixed and did not change

Question 8

What is the induced fit?

Answer 8

As the substrate forms bonds with the amino acids in the active site,

the tertiary structure changes to ensure the active site forms perfects to the substrate.

Question 9

Explain why enzymes are specific to their substrate.

Answer 9

Molecules that are not the substrate can’t form the correct bonds to the amino acids in the active site.
Therefore the tertiary structure of the enzyme does not change, so the shape of the active site does not adjust to fit the model.

Question 10

What does RoR depend on?

Answer 10

Rate depends on the frequency of successful collisions between the substrate and the active site of the enzyme

Question 11

Why does the RoR increase as we increase the temperature?

Answer 11

This is because kinetic energy increases for the enzyme and substrate.

Because they are moving more rapidly the frequency of collisions between the substrate and the active site increases.

Question 12

What is the optimum temperature?

Answer 12

Maximum frequency of collisions

Question 13

How do enzymes denature when its too hot.

Answer 13

Enzymes are vibrating more rapidly. This causes hydrogen bonds etc to break. Tertiary structure changes. No longer complementary to substrate. Substrate can no longer fit in active site.

Question 14

Why can’t enzymes renature?

Answer 14

Tertiary structure has changed so much it can’t be reversed

Question 15

What is a temperature coefficient.

Answer 15

Rate of reaction at X + 10/ Rate of reaction at temperature X

Question 16

Why is the coefficient usually two?

Answer 16

The rate of an enzyme controlled reaction doubles if we increase by 10 degrees

However above the optimum temperature enzymes denature.

Question 17

What is a pH affected by?

Answer 17

Concentration of H+ ions

Question 18

How can an pH affect an enzymes

Answer 18

RoR decreases away from optimum pH

Hydrogen ions can bond with the R groups of the amino acids in the protein

This can form temporary bonds to the substrate, prevents the R groups bond to the substrate.

Hydrogen ions can also bond with the R groups on amino acids in the rest of the enzyme molecules.

This can break the bond holding the tertiary structure in place.

Question 19

Effect of increasing the substrate concentration irreversible competitive inhibitors.

Answer 19

Some irreversible competitive inhibitors bind permanently to the active site. Increasing the substrate concentration will no increase RoR.

Question 20

Difference between non-competitive and competitive.

Answer 20

NON-COMPETITIVE INHIBITORS do NOT bind to the active site of an enzyme.

Instead they bind to the allosteric site, which causes the tertiary structure to change so the active site changes

DOES NOT have a similar shape to the substrate

Question 21

Effect of increasing the substrate concentration on NON competitive inhibitors.

Answer 21

RoR is still reduced by the same amount

Non-competitive inhibitor cause the shape of the active site to change so the substrate molecules still cannot bind successfully.

Question 22

What is a metabolic pathway?

Answer 22

Series of reactions all catalysed by enzymes.

Question 23

What is end product inhibition an example of?

Answer 23

Negative feedback
Non-competitive inhibition (takes place on the allosteric site)

Question 24

What is a cofactor?

Answer 24

a non-protein compound required for the enzyme’s activity to occur

Eg. Chloride ions help amylase catalyse reactions.

Question 25

What is a coenzyme

Answer 25

Cofactors that are large organic molecules.

Question 26

What is a prosthetic group?

Answer 26

Cofactors that are permanent parts of the enzymes structure