Enzymes

Question 1

What are enzymes?

Answer 1

Biological catalysts

Question 2

What does an enzyme do?

Answer 2

Increase rate of reaction by providing a pathway of lower activation energy to get reactants to products

Question 3

What does lysozyme do?

Answer 3

Catalyses the cutting of polysaccharide chains

Question 4

What happens when you increase substrate concentration?

Answer 4

Reaction velocity increases

Question 5

What is the maximum rate of reaction called?

Answer 5

Vmax

Question 6

What is Km?

Answer 6

The substrate concentration required for half maximum velocity

Question 7

What is PHOSPHO1?

Answer 7

Found in osteoblasts and chondrocytes

Question 8

What are the two classifications of enzyme inhibitors?

Answer 8

Irreversible and reversible

Question 9

What are irreversible enzyme inhibitors called?

Answer 9

Inactivators

Question 10

What are reversible enzyme inhibitors called?

Answer 10

Competitive and allosteric

Question 11

Describe irreversible inhibition?

Answer 11

React with the enzyme and form a covalent adduct with the proteins

Question 12

What is the primary mechanism of action of diisopropyl fluorophosphate?

Answer 12

Inhibition of acetylcholinesterase (AChE)

Question 13

What does AChE do?

Answer 13

Degrades the neurotransmitter ACh

Question 14

What happens if there is too many ACh?

Answer 14

Overstimulation of receptors ion the post synaptic membrane

Question 15

What is aspirin?

Answer 15

Antipyretic, anti-inflammatory and analgesic

Question 16

What does aspirin do?

Answer 16

Irreversibly inhibiting cylooxygenase-1 (COX-1)

Question 17

What does COX-1 do?

Answer 17

Catalyses the conversion of arachidonic to prostaglandin H2 (precursor for synthesis of inflammatory mediators)

Question 18

Where does aspirin bind?

Answer 18

On the serine residue close to the active site preventing the substrate arachidonic acid from binding

Question 19

Describe competitve inhibition

Answer 19

Competes for active site of the enzyme

Like a key that gets through the keyhole but cannot unlock the door

Question 20

What is 4-aminobenzoic caid?

Answer 20

What folic acid is synthesized from

Question 21

What is used to competitively inhibit the synthesis of folic acid?

Answer 21

Sulphonamides

Question 22

What happens to Km when you introduce a competitive inhibitor?

Answer 22

Km increases

Question 23

Describe allosteric inhibition

Answer 23

Never bind to the active site

Change in conformation, substrate can longer bind

Question 24

What happens to Vmax and Km in allosteric inhibition?

Answer 24

Vmax decreases

Km often (but not always) increases

Question 25

What are the two types of allosteric inhibition?

Answer 25

Mixed and non-competitive

Question 26

What happens to the Vmax and Km in mixed allosteric inhibition?

Answer 26

Vmax decreases

Km increases

Question 27

What happens to the Vmax and Km in non-competitive allosteric inhibition?

Answer 27

Vmax decreases

Km is unchanged

Question 28

What does phophofructokinase do?

Answer 28

Catalyses transfer of phosphate from ATP to fructose 6-phosphate

Question 29

What happens when ATP is not needed?

Answer 29

The inhibitory site of PFK will be filled