Chapter 3A : Enzymes

Question 1

Define enzymes.

Answer 1

Enzymes are molecules that act as biological catalysts to increase the rate of reactions that occur in living organisms. They are not consumed during the biological reaction.

Question 2

What are enzymes made of?

Answer 2

Proteins.

Question 3

Name the monomers of proteins.

Answer 3

Amino acids.

Question 4

Describe the structure of an amino acid.

Answer 4

amine group (NH3) -N- carboxyl group (COOH)/R-group/Hydrogen

Question 5

What type of protein is an enzyme, according to its structure?

Answer 5

Tertiary level.

Question 6

State the function of enzymes.

Answer 6

Enzymes can break a single structure into two components, or join two or more components together. Enzymes increase the rate of these reactions in living organisms.

Question 7

True or False.
Each enzyme has a specific amino acid sequence, and therefore a specific 3D shape, and an active site that has a specific 3D shape.

Answer 7

True.

Question 8

Why are enzymes important for chemical reactions to occur in living organisms?

Answer 8

Because enzymes are organic catalysts, they speed up the rate of biological reactions in living organisms. Without enzymes, the metabolic reactions would occur too slowly and the temperature and pH of the body life cannot be sustained.

Question 9

True or False.

All the metabolic reactions in living organisms are controlled by enzymes.

Answer 9

True.

Question 10

Explain how temperature can affect the rate of reaction of an enzyme catalyzed reaction.

Answer 10

Enzyme activity increases with temperature, until the temperature is too high for the enzyme to function, and enzyme denaturation occurs.

Question 11

Explain how pH can affect the rate of reaction of an enzyme catalyzed reaction.

Answer 11

Enzymes are found in very diverse pH conditions, and any extremes of pH away from the enzyme optimum for that specific enzyme can result in enzyme denaturation.

Question 12

Explain how substrate concentration can affect the rate of reaction of an enzyme catalyzed reaction.

Answer 12

The rate of reaction will increase with an increase in enzyme concentration, provided that there is a non-limiting amount of substrate and cofactors.

Question 13

Explain how enzyme concentration can affect the rate of reaction of an enzyme catalyzed reaction.

Answer 13

The rate of reaction will increase and plateaus with an increase in substrate concentration, provided that there is a limited amount of enzymes.

Question 14

Explain how inhibitors can affect the rate of reaction of an enzyme catalyzed reaction.

Answer 14

The rate of reaction will decrease with an increase in inhibitors.

Question 15

Define cofactors.

Answer 15

Cofactors are the non-protein component of an enzyme.They can be organic (coenzymes) or inorganic, such as ions. They can be permanently or temporarily attached to the enzyme.

Question 16

Define coenzymes.

Answer 16

When cofactors are organic molecules, they are called coenzymes, such as vitamins.

Question 17

True or False.

All enzymes require cofactors to be active.

Answer 17

False.

Question 18

What are permanently attached cofactors called?

Answer 18

The prosthetic group.

Question 19

Explain what happens to an enzyme in high temperatures and in low temperatures.

Answer 19

At high temperatures, enzymes are no longer able to function and enzyme denaturation occurs.
At low temperatures, enzymes have little activity.

Question 20

Explain what happened to a denatured enzyme.

Answer 20

A denatured enzyme is no longer able to function as the active site has completely changed due to the extremes in temperature. The enzyme will also not be able to regain its function when the temperature does decrease.

Question 21

Define enzyme inhibitors.

Answer 21

Enzyme inhibitors can deactivate enzymes.

Question 22

Name and define the two types of enzyme inhibitors.

Answer 22

-Reversible inhibitor
Are used to control enzyme activity. There is often an interaction between the substrate or end product and the enzymes controlling the reaction.
-Irreversible inhibitor
Bind tightly and permanently to the enzymes, destroying their catalytic activity. They usually covalently modify an enzyme.

Question 23

Name the three sub-types of reversible inhibitors.

Answer 23

Competitive and non-competitive inhibition.

Question 24

Describe competitive and non-competitive inhibition

Answer 24

Competitive inhibitor blocks the active site of the enzyme, resulting in the substrate being unable to bind to the active site.
Non-competitive inhibitors works either to slow down the rate of reaction, by binding to a site other than the active site, or by blocking the active site altogether and prevent its functioning (allosteric inhibition).

Question 25

Describe the lock and key model.

Answer 25

This model proposes that the substrate is simply drawn into a closely matching cleft on the enzyme molecule.

Question 26

Describe the induced fit model.

Answer 26

This model proposes that the the enzyme changes its shape, forcing the substrate molecule to combine. The resulting product is released and the enzyme returns to its normal shape.