Enzymes and Metabolism

Question 1

Catalysts

Answer 1

chemical which:
-speeds up the rate of a chemical reaction
-remains itself unaltered at the end of the reactions
-lowers the activation energy(energy required to start the reaction)

Question 2

Lock and Key Theory

Answer 2

The shape of the active site is complimentary to the shape of the substrate

Question 3

Induced Fit

Answer 3

The active site of an enzymes is flexible and dynamic

Question 4

Induced Fit

Answer 4

-occurs when the active site changes shape to better fit the substrate after the substrate binds
-substrate molecules have a high affinity for the active site and products have low affinity allowing them to leave the active site

Question 5

Affinity

Answer 5

means the measure of the attraction between 2 objects

Question 6

Explain the relationship between the active site and reactant orientation

Answer 6

-the shape of the active site determines the orientation of the reactant. The reactants orientate themselves in the correct way to fit the active site

Question 7

Explain the relationship between the active site and activation energy

Answer 7

Active site holds the substrate, with high affinity, in an induced fit. The new shape of the active site lowers the activation energy as the substrate fits better.

Question 8

Enzyme Activity

Answer 8

-Substrate binds to the active site of the enzymes
-The shape of the active site is complimentary in that to the shape of the substrate
-The binding of the correct substrate brings about the change to the shape of the active site
-The new shape is a better fit which makes the reaction lower activation energy/temperature needed to start.

Question 9

Factors affecting enzyme activity

Answer 9

-temperature
-ph
-substrate concentration
-inhibitors:
-competitive
-non competitive

Question 10

Temperature

Answer 10

-Enzymes are more active as temperature increases
-Most active at their optimum temperature
-(optimum temp in most animal enzymes is 37 degrees)
-After the optimum temperature for the enzymes DENATURES(shape of the active site changes)

Question 11

pH

Answer 11

-Each enzyme has a working range. Outside this range the enzyme is inactive.
-An enzyme has an optimum pH.
-Either side of the optimum pH the enzyme will not work so well.

Question 12

Substrate Concentration

Answer 12

-Increasing substrate concentration increases reaction rate as more and more active site become involved
-At low substrate concentration the reaction rate is low since there are too few substrate molecules to make maximum use of all active sites.
-Reaction rate levels off as there is no further increase in enzyme activity since all active site have become involved.

Question 13

Inhibitors

Answer 13

-An inhibitor acts by slowing down / stopping the rate at which an enzyme controlled reaction can work.

Question 14

Competitive inhibitors

Answer 14

Competitive inhibitors bind at the active site preventing the substrate from binding.This decreases reaction rate. This inhibition can be reversed by increasing substrate concentration

Question 15

Why can competitive inhibition be reversed by increasing substrate concentration

Answer 15

increasing the concentration of substrate will decrease the chance of inhibition binding to the enzymes’s active site

Question 16

Non-Competitive Inhibitors

Answer 16

Non-competitive inhibitors bind away from the active site but change the shape of the active site preventing the substrate from binding.This decreases reaction rate. Cannot be reversed by increasing substrate concentration

Question 17

Why can’t non-competitive inhibition be reversed by increasing substrate concentration

Answer 17

non-competitive inhibitors do not compete for the enzyme’s active site, and therefore increasing substrate concentration will not make it less likely a non-comp inhibitor will bind to the enzyme’s allosteric site.

Question 18

Anabolic Reactions

Answer 18

Build up large molecules from small molecules.They require energy

Question 19

Catabolic reactions

Answer 19

Catabolic reactions break down large molecules into smaller molecules They release energy

Question 20

Anabolic and Catabolic are integrated

Answer 20

ATP is an important link between energy-releasing and energy-consuming reactions

Question 21

Metabolic Pathways

Answer 21

Metabolic pathways normally consist of several stages which are each regulated by a specific enzymes.
The pathway can have:
-Reversible steps
-Irreversible steps
-Alternative routes

Question 22

Why is the first step in glycolis metabolic pathway of benefit to the cell?

Answer 22

It’s irreversible to maintain a low glucose concentration inside the cell to encourage diffusion of glucose into the cell

Question 23

What is the importance of the reversible step between intermediate 1 and intermediate 2

Answer 23

Prevents the build up of intermediate 2 if no more is required by the cell

Question 24

Feedback Inhibition/End product inhibition

Answer 24

Occurs when the end-product in the metabolic pathway reaches a critical concentration.The end-product then inhibits and earlier enzyme, blocking the pathway. This prevents further synthesis of the end-product.