Topic 2 - enzymes Flashcards
What are enzymes and how do they change at the end of the reaction
Enzymes are biological catalysts that speeds up the rate of reaction and remains unchanged and reusable at the end of the reaction.
What do enzymes do to the activation energy of a reaction
Enzymes lower the activation energy of a reaction
What is the lock and key model
The lock and key model proposed that each substrate is a key that only fits a specific lock or enzyme.
Describe the alternative induced fit model
Although it is very similar to the lock and key hypothesis, in this model the enzyme and substrate interact with each other:
The enzyme and its active site (and sometimes the substrate) can change shape slightly as the substrate molecule enters the enzyme
These changes in shape are known as conformational changes
The conformational changes ensure an ideal binding arrangement between the enzyme and substrate is achieved
This maximises the ability of the enzyme to catalyse the reaction
What structure gives enzymes it’s specificity
The specificity of enzymes is due to the tertiary structure of its active site, allowing complementary binding to substrates.
Enzymes catalyse both intracellular and extracellular reactions which determine (1…)
1 - structures and functions from cellular to whole organism level.
Is catalase intra or extra cellular and what does it do (and does it require a cofactor)
Catalase intracellularly breaks down hydrogen peroxide into water and oxygen
No cofactor
Is amylase intra or extra cellular and what does it do (and does is require a cofactor)
Amylase is secreted from the salivary glands and pancreas to extracellularly break down starch.
Requires Cl- cofactor
Is trypsin intra or extra cellular and what does it do (and does is require a cofactor)
Trypsin is secreted from the pancreas to extracellularly break down proteins
No cofactor
Some enzymes are synthesised in an (1)
1 - inactive precursor form
What needs to happen if an enzyme is synthesised in an inactive precursor form
Some enzymes are synthesised in an inactive precursor form and need to be activated e.g. another enzyme removes part of the molecule in trypsin, forming the correct active site shape
Some enzymes require a cofactor, what is a cofactor?
A substance which must be present to enable an enzyme to catalyse a reaction at the appropriate rate.
what is a prosthetic group and give an example
A prosthetic group is the non-amino acid component that is part of the structure of the heteroproteins or conjugated proteins, being tightly linked to the apoprotein.
A prosthetic group is permanently bound e.g. Zn^2+ bound to carbonic anhydrase CO2 ⟷ H2CO3 ⟷ H^+ + HCO3
What do coenzymes form and what are they derived from
A coenzyme forms temporary associations and are derived from vitamins.
What are coenzymes
A coenzyme is defined as an organic molecule that binds to the active sites of certain enzymes to assist in the catalysis of a reaction.
State 4 factors that affect enzyme activity and how it affects it
pH
As pH increases, so does enzyme activity until the optimal pH is reached. Past this point, the enzyme denatures and therefore enzyme activity decreases till 0
Temperature
As temperature increases, so does enzyme activity until the optimal temperature is reached. Past this point, the enzyme denatures and therefore enzyme activity decreases till near 0
Enzyme concentration
As enzyme concentration increases, so does rate of reaction
Substrate concentration
As substrate concentration increases, so does rate of reaction until the point of saturation is reached at which point the graph plateaus and increasing concentration no longer affects reaction rate.
Draw a graph showing the rate of reaction / substrate concentration with 3 lines:
(1) enzyme controlled reaction without an inhibitor
(2) same reaction with a competitive inhibitor
(3) same reaction with a non competitive inhibitor
1 - curve that plateaus at top
2 - slightly lower than first and plateaus further along to the right but lower generally
3 - way lower and never reaches the same plateau as the other two curves (less than half the amplitude)
Describe what a competitive inhibitor is
A competitive inhibitor is any compound which closely resembles the chemical structure and molecular geometry of the substrate. The inhibitor competes for the same active site as the substrate molecule. The inhibitor may interact with the enzyme at the active site, but no reaction takes place.
Describe what a non competitive inhibitor is
The noncompetitive inhibitor reacts either remotely from or very close to the active site. The net effect of a noncompetitive inhibitor is to change the shape of the enzyme and thus the active site so that the substrate can no longer interact with the enzyme to give a reaction.
What is the temperature coefficient
The temperature coefficient (Q10) for a specific reaction is the effect of a 10°C rise in temperature on the rate of the reaction
Give the equation of the temperature coefficient
Q10 = [rate of reaction at (T+10)C] / rate of reaction at T C
