Enzymes Flashcards
What is the job of enzymes?
They are biological catalysts, increase the rate of reactions by lowering the activation energy of the reaction they catalyse.
What is the active site?
The active site is the area of the enzyme where the reaction with the substrate takes place
-enzymes are specific to substrates they bind to so only one type of substrate fits into the enzyme active site) complementary
What is the induced fit model?
• when the enzyme and substrate form a complex
The structure of the enzyme is altered so the active site of the enzyme fits around the substrate
Factors affecting the rate of enzyme controlled reaction
1) the rate of reaction increases as enzyme concentration increases, as there are more active sites for substrates to bind to. However, increasing the enzyme concentration beyond a certain point has no effect on the rate of reaction as there are more active sites then substrates so substrates become a limiting factor
2)substrate concentration, as concentration of substrate increases, rate of reaction increases as more enzymes-substrate complexes are formed.However, beyond a certain point, the rate of reaction no longer increases as enzyme concentration becomes a limiting factor
3)Temperature, rate of reaction increases up to the optimum temperature, which is the temperature as which enzymes work at their maximum rate. Rate of reaction decreases above the optimum temperature
What are inhibitors?
A substance which slows down or stops a reaction by affecting the binding of the substrate to the enzyme.
Inhibitors can either be reversible or irreversible
Irreversible inhibitors
•heavy metal ions such as mercury, silver which cause disulphide bonds within the protein structure to break, causing the active site shape to change, thus affecting protein activity
Reversible
•bind with the active site through hydrogen bonds and weak ionic interactions, therefore they dont bind permanently. Reversible inhibitors can either be competitive or non-competitive
Competitive inhibitors
•similar to the structure of the substrate molecule, so they bind to the active site of the enzyme, decreasing its activity as they compete with substrate for the enzyme.The amount of product formed remains the same, however the rate at which product formation occurs decreases
—> the higher the concentration of competitive inhibitors the lower the reation rate
Increasing the substrate reverses the effect of competitive inhibitors by outcompeting them
Non-competitive inhibitors
• does not bind to the active site: it binds to an area on one enzyme called allosteric site
Binding of the non-competitive inhibitors change the shape of the active site preventing the binding of the substrate, increasing the conc of substrate has no affect on non-competitive inhibitors
How to differentiate between non-competitive and competitive inhibitors?
•if the rate of the enzyme controlled reaction remains low even if the substrate conc is increased, it is non-competitive inhibition
• if the rate of the enzyme controlled reaction increases when the substrate conc increases, then it is competitive inhibition
What are coenzymes?
A non-protein compound required for the enzymes activity to occur. They are organic cofactors which DO NOT bind permanently
•they facilitate the binding of substrate to enzyme
How does enzyme concentration affect the rate of reaction?
-the rate of reaction increases as enzyme concentration increases as there are more active sites for substrates to bind to,however increasing the enzyme concentration beyond a certain point has no effect on the rate of reaction
as there are more active sites than substrates so substrate concentration becomes the
limiting factor
How does substrate concentration affect the rate of reaction?
as concentration of substrate increases, rate of reaction
increases as more enzyme-substrate complexes are formed. However, beyond a
certain point the rate of reaction no longer increases as enzyme concentration
becomes the limiting factor
How does temperature affect the rate of reaction?
rate of reaction increases up to the optimum temperature, which is
the temperature at which enzymes work at their maximum rate. Rate of reaction
decreases above the optimum temperature
