Enzymes 2

Question 1

What are co-factors?

Answer 1

Non-protein factors which are essential for enzyme activity

Question 2

What are coenzymes?

Answer 2

Carbon containing cofactors (organic) derived from water soluble vitamins

Question 3

What are prosthetic groups?

Answer 3

Tightly bound cofactors

some covalently bound

Question 4

What are co-substrates?

Answer 4

Loosely + transiently bound cofactors

Question 5

What is a haloenzyme?

Answer 5

Enzyme w/ prosthetic group

Question 6

What is an apoenzyme?

Answer 6

Enzyme w/out prosthetic group

Question 7

What are the 3 cofactor examples and their roles in catalysed reactions?

Answer 7

Iron & copper
- REDOX

Zinc
-helps bind NAD

Question 8

What are the 4 coenzyme examples?

Answer 8

Biotin

Coenzyme A

NAD
-carries electrons
FAD
-carries electrons

Question 9

What are the 3 prosthetic groups?

Answer 9

Heme

Flavin

Retinal

Question 10

What is the overall pattern in the structure of coenzymes?

Answer 10

Adenine + ribose + 2 phosphates + vitamin

Question 11

What is the general structure of a cofactor?

Answer 11

Common motif of adenine + ribose + another group

Question 12

What do coenzymes do?

Answer 12

Bind to active site of enzyme + are involved in catalysis

Question 13

By how much to enzymes increase the rate of reaction?

Answer 13

10^5 to 10^17 fold

Question 14

What are steady-state kinetics?

Answer 14

The state reached a short time after mixing an enzyme + a substrate

Question 15

What is a katal?

Answer 15

SI unit

Amount of enzyme that gives 1 Mol/sec

Question 16

What is added to an enzyme assay to stop a reaction?

Answer 16

Acid

- denatures enzyme

Question 17

How can product be measured in a direct assay?

Answer 17

If P is coloured - measure colour change via spectrophotometer

P could fluoresce or be a gas

Measure continuously

Question 18

How is rate of reaction measured in a discontinuous direct assay?

Answer 18

Stop reaction (using acid/alkali) at set time points + measure P or S

Question 19

What are the 4 factors that affect enzyme rate?

Answer 19

Conc of enzyme
Conc of substrate
Temp
pH

Question 20

When is there a linear relationship between rate + amount of enzyme?

Answer 20

When substrate is not limiting or product in excess

Question 21

What happens as substrate conc increases?

Answer 21

Rate increases by lesser amounts
–> eventually reaches plateau
= Vmax

Question 22

What is the Michaelis-Menten equation?

Answer 22

V = Vmax[S] / (Km +[S])

Question 23

What is Km?

Answer 23

Michaelis constant
= the [S] that gives 1/2 maximal rate
= 1/2Vmax

Question 24

The higher the Km…?

Answer 24

The higher the [S] needed to reach Vmax

Question 25

Why could the real Km of some enzymes be different to those found in experiments?

Answer 25

In labs, artificial substrates added to enzymes | - could be different for natural substrates

Question 26

What is the issue with the Lineweaver-Burk equation rearrangement?

Answer 26

The lowest [S] gives the highest values on the graph | --> but lowest [S] are most inaccurate values

Question 27

Why does reaction rate increase w/ temp up to optimum?

Answer 27

Increases enzyme's internal mobility --> allows substrate to enter + exit active site as allows formation of transition state complex

Question 28

Why does rate of reaction decrease w/ temp beyond optimum?

Answer 28

Enzyme too mobile --> loses structure = denatured

Question 29

What are isozymes?

Answer 29

Different forms of enzymes w/ same function but diff structure

Question 30

How does pH affect enzymes?

Answer 30

H+ ions bind to/are released from carboxyl groups + amino groups present in side chains of amino acids --> charges on amino acids are important for structure

Question 31

What are the water soluble vitamins?

Answer 31

``` B1, B2, B3, B6 + B12 Vit C Folic acid Biotin Pantothenic acid ```

Question 32

What are the water insoluble vitamins?

Answer 32

A D E K

Question 33

Which type of vitamins form co-factors?

Answer 33

Water soluble

Question 34

Which test is used to measure glucose?

Answer 34

Hardings test | in a discontinuous direct assay (measure green colour)