Chapter 6b

Question 1

Small amount of energy input required in order for chemical reactions to occur

Answer 1

Activation energy

Question 2

Substance that helps a chemical reaction to occur

Answer 2

Catalyst

Question 3

special molecules that catalyze biochemical reactions

Answer 3

enzyme

Question 4

Chemical reactants to which an enzyme binds

Answer 4

Substrate

Question 5

Alteration of the natural properties on an enzyme and render it weak or ineffective

Answer 5

Denaturation

Question 6

Inorganic helper ions such as iron or magnesium

Answer 6

Cofactor

Question 7

Organic helper molecules such as Vitamin C

Answer 7

Coenzyme

Question 8

What factors determine the rate of an enzymatic reaction?

Answer 8

Activation energy typically through heat energy

Question 9

Does a higher activation energy result in a faster or slower reaction rate?

Answer 9

Higher the activation energy, the slower the reaction will be

Question 10

What is the source of activation energy for most chemical reactions?

Answer 10

Heat energy

Question 11

Why does increased temperature increase the rates of reaction?

Answer 11

Heat speeds up the motion of molecules, causing them to collide with more force, and more often

Question 12

Cellular reactions cannot use heat energy from their surroundings as activation energy. Why not?

Answer 12

The activation energies for most cellular reactions are too high for heat energy from the surroundings to overcome

Question 13

How does an enzyme catalyze a reaction? How does it lower the activation energy?

Answer 13

They lower the activation energy by binding to the reactant molecules and holding them in such a way as to make the chemical bond-breaking and bond-forming process easier

Question 14

What is the “active site” and what properties give it it’s specificity?

Answer 14

The place on the enzyme where the substrate binds; there is a unique combination of R-groups present at an enzyme’s active site

Question 15

What are some benefits and some drawbacks of having a high level of specificity?

Answer 15

It is vulnerable to environmental influences that alter it’s structure but it is for a specific chemical reaction

Question 16

Name some environmental changes that might denature an enzyme.

Answer 16

Temperature, pH

Question 17

What is the “lock and key” model?

Answer 17

The idea that the enzyme active site and substrate fit together perfectly in one step

Question 18

How does the lock and key model differ from the “induced fit” model?

Answer 18

In the induced fit, the enzyme and substrate are specific to each other, but also undergo changes in their conformation upon binding

Question 19

What happens to enzymes once they have catalyzed a reaction?

Answer 19

It will always return to its original state at the completion of the reaction

Question 20

What is competitive inhibition? How does it help regulate enzyme activity and therefore chemical reaction rate?

Answer 20

An inhibitor molecule is similar enough to the substrate that it can bind to the active site and block the substrate from binding; the inhibitor molecule competes with the substrate for active site binding

Question 21

What is non-competitive inhibition? How does it differ from competitive inhibition?

Answer 21

An inhibitor molecule binds to the enzyme in a location other than the active site; activity of the enzyme is greatly reduced

Question 22

What is allosteric inhibition? How does it help regulate enzyme activity?

Answer 22

An inhibitor molecule binds to the enzyme in a location other than the active site, resulting in reduced affinity of the enzyme for its substrate; cause slight conformational changes at the active site so substrate bind less efficiently

Question 23

How does allosteric inhibition differ from allosteric activation?

Answer 23

Inhibition makes the substrate bind less efficiently and activation makes the substrate bind more efficiently

Question 24

What is the purpose of cofactors and coenzymes? How are they similar? How are they different?

Answer 24

Several enzymes don’t work well, or at all, unless they are also bound by specific non-protein helper molecules; cofactors are inorganic and coenzymes are organic

Question 25

How do cofactors and coenzymes assist in the regulation of enzymatic reactions?

Answer 25

Several enzymes don’t work well, or at all, unless they are also bound by specific non-protein helper molecules

Question 26

Give an example of “compartmentalization” of enzymes. How is this used by eukaryotic cells to regulate chemical reactions?

Answer 26

Metabolic enzymes in the mitochondria; or digestive enzymes in lysosomes; enzymes required only for certain cellular processes can be housed separately inside structures along with their substrates

Question 27

Give an example of compartmentalization of enzymes.

Answer 27

Metabolic enzymes in the mitochondria; or digestive enzymes in lysosomes

Question 28

What is “feedback inhibition?” Give examples of feedback inhibition in cellular respiration.

Answer 28

The use of a reaction product to regulate its own further production; the cellular production of amino acids and nucleotides