Enzyme Activity: Kinetics and Inhibition

Question 1

What increases the rate of reaction?

Answer 1

Temperature
Concentration
Enzymes

Question 2

How do enzymes increase the rate of reaction?

Answer 2

By lowering the activation energy needed.

Question 3

What are some important features of enzymes?

Answer 3

Highly specific
Unchanged after the reaction
Do not affect the reaction equilibrium
Increase rate of reaction
Proteins
May require associated cofactors.

Question 4

Why are we interested in enzymes?

Answer 4

Inheritable genetic disorders
Overactive enzymes can cause disease
Measurement of enzyme activity for diagnosis
Inhibition of enzymes by drugs

Question 5

What is the active site of an enzyme?

Answer 5

The place where the substrate bind on an enzyme for the chemical reaction to occur.

Question 6

What are the substrates bound to in the active site of the enzyme?

Answer 6

By multiple weak bonds. All types of non-covalent bonds.

Question 7

What is the maximal velocity of enzymatic activity?

Answer 7

When all the enzymes’ active sites are occupied at all times. This is only a theoretical value.

Question 8

What is Km?

Answer 8

The Michaelis constant. The substrate concentration that gives half the maximal velocity.

Question 9

What is affinity?

Answer 9

How well or strong a substrate binds to an enzyme.

Question 10

What does a low Km means in terms of affinity?

Answer 10

Low Km means high affinity for substrate. Not a high concentration is needed to achieve half of Vmax.

Question 11

What does a high Km mean?

Answer 11

Means low affinity for substrate. A higher concentration is needed to achieve half of Vmax.

Question 12

If we double the amount of enzymes, what happens to the rate?

Answer 12

It doubles as well. The rate of an enzyme catalysed reaction is proportional to the concentration of enzyme.

Question 13

What is the Lineweaver-Burk plot?

Answer 13

When the Michaelis-Menten equation is rearranged into a linear plot.

Question 14

Why can the Lineweaver-Burk plot be useful?

Answer 14

Because it allows easier estimation of Km and Vmax.

Question 15

Look at page 19 for the Lineweaver-Burk plot.

Answer 15

Yup.

Question 16

Explain what enzyme inhibitors are.

Answer 16

Molecules that slow down or prevent an enzyme reaction.

Question 17

What types of enzyme inhibitors are there?

Answer 17

Irreversible inhibitors
Reversible inhibitors (2 types):
Competitive reversible
Non-Competitive reversible

Question 18

What are features of irreversible inhibitors?

Answer 18

Bind very tightly generally by covalent bonds and it’s very hard to get them off.
Examples such as nerve gases such as sarin.

Question 19

What are features of reversible inhibitors?

Answer 19

Bind not very tightly by non-covalent bonds. They dissociate easily.

Question 20

What are features of competitive inhibitors?

Answer 20

Binds at the active site. This affects Km but not Vmax. This means lower affinity for the substrate.

Question 21

What are features of non-competitive inhibitors?

Answer 21

Binds somewhere else than the active site. Affects Vmax but not Km.

Question 22

Look at page 22 and page 24 to understand what happens during inhibition.

Answer 22

Yup.