Enzymes and Metabolism Flashcards
Catalysts
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)
Lock and Key Theory
The shape of the active site is complimentary to the shape of the substrate
Induced Fit
The active site of an enzymes is flexible and dynamic
Induced Fit
-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
Affinity
means the measure of the attraction between 2 objects
Explain the relationship between the active site and reactant orientation
-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
Explain the relationship between the active site and activation energy
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.
Enzyme Activity
-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.
Factors affecting enzyme activity
-temperature
-ph
-substrate concentration
-inhibitors:
-competitive
-non competitive
Temperature
-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)
pH
-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.
Substrate Concentration
-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.
Inhibitors
-An inhibitor acts by slowing down / stopping the rate at which an enzyme controlled reaction can work.
Competitive inhibitors
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
Why can competitive inhibition be reversed by increasing substrate concentration
increasing the concentration of substrate will decrease the chance of inhibition binding to the enzymes’s active site
Non-Competitive Inhibitors
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
Why can’t non-competitive inhibition be reversed by increasing substrate concentration
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.
Anabolic Reactions
Build up large molecules from small molecules.They require energy
Catabolic reactions
Catabolic reactions break down large molecules into smaller molecules They release energy
Anabolic and Catabolic are integrated
ATP is an important link between energy-releasing and energy-consuming reactions
Metabolic Pathways
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
Why is the first step in glycolis metabolic pathway of benefit to the cell?
It’s irreversible to maintain a low glucose concentration inside the cell to encourage diffusion of glucose into the cell
What is the importance of the reversible step between intermediate 1 and intermediate 2
Prevents the build up of intermediate 2 if no more is required by the cell
Feedback Inhibition/End product inhibition
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.
