Enzyme kinetics

Question 1

What is enzyme kinetic?

Answer 1

Discipline focused on determining the rate of reaction and how it changes in response to changes in experimental parameters

Question 2

What is the rate enzymatic reaction affected by?

Answer 2

Enzyme
Substrate
Effectors
Temperature

Question 3

What is Kcat?

Answer 3

Enzyme turnover number
Number of times each enzyme site converts substrate to product per unit time

Question 4

What does the Kcat describe?

Answer 4

The number of times each enzyme site converts substrate to product per unit time for a given enzymes concentration

Question 5

What is Km

Answer 5

Concentration at 1/2 Vmax

Question 6

What does Km tell you?

Answer 6

Affinity
Low Km high affinity
High Km low affinity

Question 7

How do you measure efficiency of an enzyme?

Answer 7

Kcat/Km

Question 8

How are affinity and specificity related?

Answer 8

More specific higher affinity

Question 9

2 types of substrate reactions when 2 or more reactants are involved

Answer 9

Sequential reactions
Double displacement reactions

Question 10

2 ways of sequential reactions

Answer 10

Random or ordered

Question 11

Different name for double replacement reaction

Answer 11

Ping-pong

Question 12

Different name for irreversible inhibitors

Answer 12

Inactivators

Question 13

What can reversible inhibitors bind to?

Answer 13

Free enzyme (prevent binding of substrate)
Enzyme-substrate complex (prevent reaction)

Question 14

What are reversible inhibitors often?

Answer 14

Structural analogs of substrates or product

Question 15

Are irreversible inhibitors competitive?

Answer 15

No

Question 16

How is the velocity of an enzymatic reaction calculated?

Answer 16

Measuring the quantity of substrate transformed per unit time or products formed by the reaction

Question 17

Which inhibitors are competitive?

Answer 17

Reversible

Question 18

What can you measure the formation of product with when mixing an enzyme and substrate?

Answer 18

Spectrophotometer

Question 19

What is the affinity with the enzyme when the Km is low?

Answer 19

High, need less substrate to get to 1/2 Vmax

Question 20

What is the affinity with the enzyme when the Km is high?

Answer 20

Low, need more substrate to get to 1/2 Vmax

Question 21

What does a high ratio between Kcat and Km say about the efficiency?

Answer 21

High efficiency

Question 22

Is high efficiency of an enzyme always a good thing?

Answer 22

No it depends on the enzyme and it’s function

Question 23

What can a non-linear Michaelis-Meenten plot be used to calculate?

Answer 23

Km and Vmax

Question 24

What is the slope in a Lineweaver-burk plot?

Answer 24

Km/Vmax

Question 25

What is Km used as a measure of?

Answer 25

An Enzyme’s affinity for its substrate

Question 26

What happens to Vmax when enzyme concentration is doubled?

Answer 26

It is also doubled

Question 27

What happens to Km when enzyme concentration is doubled?

Answer 27

Remains the same, is independent of enzyme concentration

Question 28

What does the lineweaver-burk plot?

Answer 28

The Michaelis Menten equation

Question 29

2 possible scenarios when having a 2 substrate reaction

Answer 29

Sequential reaction
Double displacement reactions

Question 30

What is a sequential reaction?

Answer 30

Reaction where an enzyme reacts with another enzyme before reaction with a second substrate which then forms product

Question 31

What is a double displacement reaction?

Answer 31

Also called ping-pong reaction because substrates bind sequentially

Question 32

Are sequential reactions random or ordered?

Answer 32

Can be both

Question 33

Which substrate binds first in an ordered sequential reaction?

Answer 33

The leading substrate

Question 34

Which substrate binds first in a random sequential reaction?

Answer 34

Either of the substrates may bind first