Enzymes

Question 1

what are enzymes?

Answer 1

Proteins that Catalyze Chemical Reactions –> Speed up reactions without being consumed

Question 2

what does a chemical reaction involve?

Answer 2

the breaking and forming of new bonds between 2 molecules

Question 3

what is activation energy?

Answer 3

initial investment of energy needed to start all reactions

Question 4

how do enzymes speed up the rate of a reaction?

Answer 4

by lowering the energy needed to start the reaction

Question 5

what are 3 ways enzymes lower the activation energy?

Answer 5

1. provide template on which substrates come together in proper orientation
2. stretch critical bonds in substrate
3. provide an environment more conducive to a particular reaction

Question 6

what is a substrate?

Answer 6

reactant an enzyme acts on

Question 7

what is it called when an enzyme binds to its substrate(s)?

Answer 7

enzyme-substrate complex

Question 8

what happens while the enzyme and substrate are joined?

Answer 8

the enzyme catalyzes the reaction, converting the substrate to the product(s) of the reaction

Question 9

what are the six steps in the Catalytic Cycle of an Enzyme?

Answer 9

1. Substrates bind to the active site in an enzyme –> enzyme changes shape to enfold substrate
2. Substrates held in active site by weak interactions –> hydrogen bonds and ionic bonds
3. Active site can lowers activation energy and speeds up a reaction
4. Substrates are converted to products
5. products are released
6. Active site is available for two new substrate molecules

Question 10

how do enzymes control which substrates enter its active site?

Answer 10

there unique 3-D shape means that it can only bind its specific substrate(s)

Question 11

what is induced fit? what else is accomplished by this change?

Answer 11

is when the enzyme changes shape slightly in order to more tightly bind the substrate to the active site
- also works to bring R groups in active site into positions that enhance their ability to catalyze the reaction

Question 12

what determines the rate of Enzyme Catalyzed Reactions?

Answer 12

Dependent on initial concentration of substrate

Question 13

how can reaction rate be increased? when does this stop working? how else can reaction rate be increased?

Answer 13

• Increasing concentration of substrate increases reaction rate
• stops working when all enzymes are saturated
• After saturation the only way to increase reaction rate is to add more enzyme

Question 14

enzymes have optimal … and …

what happens when the environment moves away from the optimal conditions above?

Answer 14

• temperature and pH

- reaction rate decreases as optimal temperature/pH increase/decrease

Question 15

what happens if temperature falls below optimum temperature? rises above optimum temperature?

Answer 15

• slows down rate of reactions due to decrease in collisions between the enzyme and substrate(s)
• disrupts weak interactions required to maintain an enzyme’s shape

Question 16

which interactions can be disrupted by an increase in temperature?

Answer 16

hydrogen bonds, ionic bonds, and hydrophobic interactions

Question 17

what happens to an enzyme when pH is above or below optimum pH

Answer 17

• causes disruption in the weak interactions required to maintain an enzyme’s shape because it increases/decreases the amount of ions in the environment
• Lower pH = more H+ in the enzyme’s environment
• Higher pH = less H+ in the enzyme’s environment
• Both of which affect weak interactions (hydrogen bonds and ionic bonds)

Question 18

what is a cofactor?

Answer 18

non-protein helper required by an enzyme for catalytic activity - can be an inorganic molecules

Question 19

what is a coenzyme?

Answer 19

organic molecules that act as cofactors

Question 20

what are the 2 types of inhibitors?

Answer 20

1. Competitive Inhibitors

2. Noncompetitive Inhibitors

Question 21

why is selective inhibition used?

Answer 21

to control the rate of enzyme catalyzed reactions in a cell

Question 22

what are competitive inhibitors? how does it work? how can this inhibitor be overcome?

Answer 22

-Inhibitors that resemble a specific substrate
-Competes with substrate for active site and therefor reduces enzyme activity by blocking the active site
-Increasing substrate concentration can overcome
this type of inhibition

Question 23

what are non-competitive inhibitors? how does it work? can this inhibitor be over come by the same method as competitive inhibitors?

Answer 23

-inhibitors that do not directly compete with a substrate for the active site
-binds to another site on the enzyme and causes a change in the shape of the active site, which makes the substrate no longer capable of binding to the active site
- no, Increasing substrate concentration has no affect on
noncompetitive inhibition, Only a decrease in the concentration of the inhibitor can increase the reaction rate

Question 24

what is feedback inhibition?

Answer 24

its when an output of a process is used as an input to control the behavior of the process itself

• a product of a chain of enzymes then becomes the inhibitor to the first enzyme in the chain, stopping the process
• Common method used to control a metabolic pathway

Question 25

why might feedback inhibition be used?

Answer 25

to Prevent cells from wasting resources by making more product than is needed