General Properties of Enzymes

Question 1

Enzymes are what types of molecules?

Answer 1

Proteins

Question 2

What do enzymes do?

Answer 2

They catalyze (increase reaction rate) biochemical reactions.

Question 3

Is an enzyme consumed and/or altered during a reaction?

Answer 3

No

Question 4

What do most chemical reactions require to proceed?

Answer 4

Energy

Question 5

Reactions must absorb enough energy to overcome ____?

Answer 5

The activation barrier

Question 6

How much energy is required to activate a reaction?

Answer 6

1 mole of energy

Question 7

What is the energy of activation?

Answer 7

The amount of energy required to activate, or bring to transition state.

Question 8

What does the ES in ES complex stand for?

Answer 8

Enzyme-substrate complex

Question 9

Once the substrate is activated, what can happen?

Answer 9

Molecules can go under conversion to product

Question 10

How do enzymes catalyze a reaction rate?

Answer 10

They provide an alternate pathway with a lower energy of activation requirement.

Question 11

What does the ES complex break down into?

Answer 11

The free enzyme and the product

Question 12

Does the ES complex have a higher or lower reactivity?

Answer 12

Higher

Question 13

What is an ES complex?

Answer 13

It is the physical binding of a substrate to the active site of an enzyme.

Question 14

What are active sites?

Answer 14

A certain area on an enzyme that shows a specificity for substrates.

Question 15

Can enzymes be specific for more than one substrate?

Answer 15

Yes

Question 16

What are the 5 factors affecting enzyme activity?

Answer 16

Temperature, pH, substrate concentration, co-factors, and time

Question 17

What is the optimum temperature for clinically significant enzymes?

Answer 17

35-39 degrees Celsius

Question 18

What effect does temperature have on enzymatic activity?

Answer 18

It increases molecular collisions and speeds up the rate of the reaction.

Question 19

How much does the enzyme reaction rate increase when temperature increases by 10 degrees Celsius?

Answer 19

Reaction rate doubles

Question 20

The enzymatic reaction rate will double when temperature (in degrees Celsius) is increased by how much?

Answer 20

10 degrees Celsius

Question 21

In the lab, at what temperatures can enzymes be measured at?

Answer 21

25 degrees, 30 degrees, and 37 degrees

Question 22

In order to stabilize the enzyme reaction rate, what must be done?

Answer 22

Maintain a constant temperature of +/- 0.1 degree Celsius

Question 23

How does pH influence enzymatic activity?

Answer 23

Influences extent of dissociation of both substrate and enzyme by changing the shape and charge.

Question 24

How does pH change the shape of an enzyme?

Answer 24

Denatures the enzyme

Question 25

How does pH change the ionic state of an enzyme?

Answer 25

Changes the charge on an amino acid residue within the active site

Question 26

Does each enzyme have a specific pH for optimum activity?

Answer 26

Yes

Question 27

How does changing the shape and or/charge of an enzyme affect the reaction?

Answer 27

Affects ability of the enzyme and substrate to attract and be bound together. This will change the reaction rate.

Question 28

What is 1st order kinetics?

Answer 28

As substrate concentration increases, the enzyme activity increases because there is more substrate to react with.

Question 29

1st order kinetics are proportional to what?

Answer 29

Substrate concentration

Question 30

What is maximum velocity (Vmax)?

Answer 30

All enzyme is saturated with substrate and any further increase of substrate concentration produces no further increase in maximum velocity.

Question 31

What is zero order kinetics?

Answer 31

Any further increase in substrate will have no effect on reaction rate.

Question 32

What is the Michaelis constant?

Answer 32

Km=(k1+k2)/k1

Question 33

What does the Michaelis constant imply?

Answer 33

It is the substrate that yields 1/2 maximum velocity.

Question 34

What does velocity depend on?

Answer 34

It depends on the enzyme amount that is bound to the substrate as the ES complex.

Question 35

When the Km value becomes smaller, what happens?

Answer 35

The attraction between enzyme and substrate becomes stronger.

Question 36

When the attraction between enzyme and substrate is stronger, will it take more or less substrate to saturate the active site of an enzyme?

Answer 36

Less substrate

Question 37

A smaller Km value will have what effect on Vmax?

Answer 37

Vmax is reached at a relatively low substrate concentration.