Enzymes

Question 1

How do enzymes accelerate reaction rates?

Answer 1

By decreasing the Activation Energy

Question 2

Where do substrates bind to on an enzyme?

Answer 2

The Active Site

Question 3

What is the Induced-Fit Model?

Answer 3

The enzyme conformation changes to accommodate the substrate

Question 4

What is the substrate for the enzyme Hexokinase?

Answer 4

Glucose

Adds a phosphate group to make glucose-6-phosphate

Question 5

What kind of bonds hold the substrate in the active site?

Answer 5

Non-covalent bonds (such as hydrogen bonds and ionic bonds)

Question 6

What type of reaction occurs when sucrose is catalysed?

Answer 6

Hydrolysis

Question 7

What enzyme catalyses sucrose?

Answer 7

Sucrase

Question 8

What bond is broken by hydrolysis when catalysing sucrose?

Answer 8

Glycosidic Bond

Question 9

What are the products when sucrose is catalysed?

Answer 9

Glucose and Fructose

Question 10

Which two amino acids are involved in breaking the glycosidic bond between sugar D and sugar E in a Lysozome catalytic reaction?

Answer 10

Glutamate 35

Aspartate 52

Question 11

How does Lysozome break the bond between sugar D and E?

Answer 11

1. Sugar D is forced into a strained conformation
2. Glu 35 donates a proton (H+)
3. Asp 52 attacks C1 which forms a covalent bond with sugar D
4. O of H20 attacks C1 which displaces Asp 52 and returns the enzyme to its original state

Question 12

What is the optimal pH for the enzyme Pepsin (stomach)?

Answer 12

pH2

Question 13

What is the optimal pH for the enzyme Trypsin (small intestine)?

Answer 13

pH8

Question 14

How does Rifampicin inhibit enzymes?

Answer 14

It binds to RNA polymerase in bacteria and prevents initiation of transcription

Question 15

What is a Competitive Inhibitor?

Answer 15

They bind to the active site of an enzyme and compete with the substrate (structurally similar to S)

Question 16

What is a Noncompetitive Inhibitor?

Answer 16

They bind to another part of the enzyme causing the enzyme to change shape so that the substrate can’t bind to the active site

Question 17

What is Feedback Inhibition?

Answer 17

It is the end product of a metabolic pathway.

It prevents a cell from wasting chemical resources by synthesising more product than is needed.

Question 18

What is the name of the enzyme that ADDS a phosphate group?

Answer 18

Protein Kinase

Question 19

What is the name of the enzyme that REMOVES a phosphate group?

Answer 19

Protein Phosphatase

Question 20

What are enzymes called when stored as inactive precursors?

Answer 20

Proenzymes or Zymogens

Question 21

How are Proenzymes activated?

Answer 21

By irreversible cleavage of 1 or more peptide bonds

Question 22

How is Fibrinogen converted into Fibrin?

Answer 22

1. Injury to a blood vessel produces a signal that converts Prothrombin to Thrombin.
2. Thrombin converts Fibrinogen to Fibrin by cleaving off A and B ends of the polypeptide chains.