BMS02-1010 Enzyme Kinetics

Question 1

At low substrate concentrations, what can you deduce about reaction rate?

Answer 1

They are directly proportional according to 1st order kinetics

Question 2

Describe zero order kinetics

Answer 2

At high substrate concentrations rate of reaction is independent according to 0 order kinetics

Question 3

What is the michaelis menton reaction model?

Answer 3

E + S ES -> E + P
K1
K-1 K2

Question 4

What are the 3 assumptions of the MM equation?

Answer 4

S is far far less then E so the amount of substrate bound at any one time is very small

ES doesn’t change with time, formation is equal to break down

Initial velocities are used as the concentration of the product is small and the backwards reaction of F to S can be ignored

Question 5

Write the michaelis-menton equation

Answer 5

V0= Vmax x (S)

Km + (S)

Question 6

V0

Answer 6

Initial reaction velocity

Question 7

Vmax

Answer 7

Maximum velocity, when all active sites are saturated

Question 8

Km equation

Answer 8

Michaelis constant (K-1 + K2) /K1

Question 9

What happens when V0=0.5?

Answer 9

0.5 (Km + (S)) = Vmax (S)

Km = (S)

Question 10

Half Vmax =

Answer 10

Km

Question 11

What happens to Km when substrate concentration is increased?

Answer 11

Km decreases

Question 12

What happens to the km equation when K2 is far smaller than the other values?

Answer 12

K-1 / K1

Question 13

What does a low km indicate?

Answer 13

High affinity for the substrate

Question 14

What is the dissociation constant of the ES complex?

Answer 14

Kd = K-1/K1

Question 15

When does km measure the affinity of the enzyme for the substrate?

Answer 15

When k2 is far smaller

Question 16

Why does km only represent affinity when k2 is very small?

Answer 16

It’s then a complex function of 3 or more rate constants

Question 17

What does Kcat mean?

Answer 17

Number of substrate converted to product in a given amount of time on a single enzyme

Question 18

How do you compare catalytic efficiency?

Answer 18

Kcat/Km - the specificity constant

Question 19

What does a high specificity number indicate?

Answer 19

A good enzyme

Question 20

What is the lineweaver-burke plot?

Answer 20

1/V0 against 1/S

Question 21

What’s the y=mx+c equation?

Answer 21

1/V0 = (Km/Vmax) x (1/S) + (1/Vmax)

Question 22

How can you use the graph to find Vmax and Km?

Answer 22

X axis = - (1/km)

Y axis = 1/Vmax

Question 23

What else can the graph tell you?

Answer 23

If the enzyme is competitive (Km changes) or non-competitive (V max changes)

Question 24

What is used in diastix

Answer 24

Glucose oxidase

Question 25

Which enzyme indicates liver damage?

Answer 25

Alanine aminotransferase

Question 26

Which enzyme indicates myocardial infarction

Answer 26

Heart isoenzyme of lactate dehydrogenase and creatine kinase LDH is better to use 48hrs after the incident as endothelial cells rupture releasing their content

Question 27

Km

Answer 27

Affinity of the enzyme

Question 28

How would the graph of an allosteric enzyme differ?

Answer 28

Its sigmoid not hyperbolic

Question 29

How is protein fructokinase regulated

Answer 29

AMP turns it on | ATP and citrate turn it off

Question 30

How is protein kinase regulated?

Answer 30

Fructose -1,6-bisphosphate

Question 31

How is glycogen phosphorylase activated?

Answer 31

Phosphorylation

Question 32

How is glycogen synthase regulated?

Answer 32

Activity is decreased by phosphorylation

Question 33

Which 3 enzymes can insulin increase the activity of?

Answer 33

Glucokinase Phosphofructokinase Pyruvate kinase

Question 34

Compare Km and Vmax of heart and muscle LDH

Answer 34

If there was lots of lactate in the heart it would kill you so it has a high affinity (low km) In the muscle there is lots of lactate so it has a low affinity so it leaves the active site quicker (high km)

Question 35

Adenylylation

Answer 35

ATP to PPi

Question 36

Uridylylation

Answer 36

UTP to PPi

Question 37

Ribosylation

Answer 37

NAD

Question 38

Acetylation

Answer 38

Transcription

Question 39

How are ACE inhibitors used to treat heart failure?

Answer 39

ACE inhibitors block the ACE enzyme so it can't convert angiotensin 1 to 2, 2 causes vasoconstriction and makes aldosterone which increases Na retention, stopping this reduces cardiac load and water retention so there's less swelling