C3: Enzymes

Question 1

What are intracellular and extracellular enzymes?

Answer 1

Intracellular -> works inside cells
Extracellular -> works outside cells

Question 2

How do enzymes speed up reactions?

Answer 2

by lowering activation energy

Question 3

What is activation energy?

Answer 3

the energy needed to start a chemical reaction

Question 4

What are the 3 ways in which enzymes lower activation energy?

Answer 4

1. binding and orienting substrates
2. rearranging electrons in a substrate
3. straining substrate and forcing it to a transition state

Question 5

What are endergonic and exergonic reactions?

Answer 5

Endergonic -> products contain more free energy than reactants
Exergonic -> products contain less free energy than reactants (releases energy in the form of heat)

Question 6

What are anabolic and catabolic reactions?

Answer 6

Anabolic -> enzymes bring the substrate molecules together
Catabolic -> enzymes break substrates

Question 7

What are the two hypotheses of enzymes’ mode of action?

Answer 7

Lock-and-key hypothesis: the substrate has to perfectly fit the active site
Induced-fit hypothesis: the enzyme/substrate can change shape to ensure a perfect fit (more efficient)

Question 8

What type of proteins are enzymes?

Answer 8

globular proteins

Question 9

What is a turnover number?

Answer 9

the number of substrate molecules transformed per second by one enzyme

Question 10

Why are enzymes present in small amounts?

Answer 10

They have high molecular activity.

Question 11

What factors affect reaction rates?

Answer 11

temperature, pH, enzyme concentration, and substrate concentration

Question 12

How does temperature affect reaction rates?

Answer 12

At low temperatures, enzymes have low kinetic energy and do not react with substrates a lot. At high temperatures, enzymes denature. Enzymes have an optimum temperature where their reaction rate is the greatest.

Question 13

What is the optimum temperature for most human enzymes?

Answer 13

40º C

Question 14

How does pH affect reaction rates?

Answer 14

Each enzyme has its own optimum pH, and extremes of pH can denature them.

Question 15

How do you measure the effect of an enzyme?

Answer 15

compare the non-catalyzed rate with the catalyzed rate

Question 16

Why do we measure the initial rate of reaction?

Answer 16

to measure before factors like substrate concentration had time to change; reflects the graph

Question 17

What is affinity?

Answer 17

The attraction of enzyme to substrate

Question 18

What are the two types of reversible inhibitors, and how do they affect the rate of reaction?

Answer 18

Competitive inhibitors compete with substrates for the active site. Non-competitive inhibitors bind to an enzyme’s allosteric site, which alters the shape of the active site.

Question 19

What are free and immobilized enzymes?

Answer 19

Free enzymes are not bound and are free to add to solutions. Immobilized enzymes are bound to a stationary and insoluble material.

Question 20

What are the three advantages of using immobilized enzymes?

Answer 20

1. There are no enzymes in the product
2. They can be reused multiple times
3. They have a greater tolerance of temperature and pH changes.