Enzyme Kinetics

Question 1

What does Vmax mean?

Answer 1

• is the maximum is when enzymes are at their highest rate and completely saturated with their substrates.
• Hence ‘V’ for velocity

Question 2

What does [S] stand for?

Answer 2

-Substrate Concentration

Question 3

What does Km mean?

Answer 3

• Michaelis Constant
• Substrate Concentration in moles where Vmax is half maximal value
• Also Rate Constant of disappearance of the Enzyme-Substrate concentration which was formed in the reaction at Activated Complex
• Shows enzyme affinity

Question 4

What is Michaelis-Mentin Model used for?

Answer 4

-Explains relationship between Km and Vmax

Question 5

What does K1 mean?

Answer 5

Rate Constant:

-K1- Rate Constant for Enzyme Association with Substrate E + S > ES Complex

Question 6

What does K2 mean?

Answer 6

Rate Constant:

• ES > E+P
• Formation of product from enzyme and substrate reacting

Question 7

What does K-1 mean?

Answer 7

Rate Constant:

-Backwards reaction when enzyme dissociates from Substrate in (ES) Complex

Question 8

What does V0 mean?

Answer 8

-Rate of product increase

Question 9

How can Vmax and KM be calculated in an experiment?

Answer 9

-Repeat at different substrate concentrations

Question 10

Why is Vmax and KM not always easy to determine?

Answer 10

-Vmax never reaches its true value

Question 11

What X2 things is the Michaelis-Mentin Equation used for?

Answer 11

• Rate of substrate catalysis

- Calculates velocity

Question 12

What can Michaelis-Mentin Equation be arranged to and what for?

Answer 12

• Straight line equation

- Lineweaver Burke Plot

Question 13

What type of curve does the Michaelis Model form?

Answer 13

-Sigmoidal

Question 14

What type of graph does the Lineweaver Burk Plot have?

Answer 14

-Straight line

Question 15

What is the relationship between the Michaelis Mentin Model and Lineweaver Burke Plot?

Answer 15

• Inverse relationship of values

- Lineweaver calculates values by 1/ Value

Question 16

Where can the Vmax and Km values be found on the Lineweaver Burke Plot?

Answer 16

• Vmax- Y Intercept

- Km- X intercept

Question 17

What does a Low Km value mean?

Answer 17

-Enzyme only needs a small amount of substrate to work at Km

Question 18

What does a High Km value mean?

Answer 18

-Enzyme needs a LARGE amount of substrate to work at its Km

Question 19

What are the two types of enzyme inhibition?

Answer 19

Reversible and Irreversible

Question 20

What are the two types of Inhibitors and which can be reversible/ irreversible?

Answer 20

• Competitive (Reversible)

- Non-Competitive (BOTH-Reversible/Irreversible)

Question 21

How does a Competitive Inhibitor work?

Answer 21

• Inhibitor binds to active site -‘Orthosteric Site’
• Prevents substrates from binding
• Inc. substrate concentration decreases competitive inhibition but can reach ‘Saturation’

Question 22

How does a Reversible Non-Competitive Inhibitor work?

Answer 22

• Inhibitor binds to another part of the enzyme

- Temporarily changes enzyme conformation so the substrate no longer fits.

Question 23

How does an Irreversible Non-Competitive Inhibitor work?

Answer 23

• Binds to enzyme and breaks covalent bonds

- Inhibitor cannot be removed

Question 24

What is Feedback Inhibition?

Answer 24

End-Product formed inhibits early stage of reaction pathway

Question 25

What is Allosteric Regulation?

Answer 25

• Enzyme regulation of non-substrate molecules binding.

- Controlled by Modulators

Question 26

What is an Allosteric Enzyme?

Answer 26

-Enzymes can change conformation and have additional sites for non-substrates to bind to.

Question 27

What are Modulators and the two types?

Answer 27

-Control Allosteric Enzymes
Positive-‘Activator’ and enhances enzyme activity
Negative- Are Inhibitors-dec. enzyme activity