NEED TO REVISE Flashcards
What is the equation for determining time in a reaction? (1)
1 / time
What is the rate in a reaction? (1)
Rate is change in absorbance over time.
What is the dependent variable? (1)
The dependant variable is the thing you measure, in this case it is the initial rate of reaction.
What is the independent variable? (1)
The independent variable is the factor you have selected from; pH, temperature, enzyme concentration and substrate concentration.
What is the control variable? (1)
The control variable will be all three factors that are not the independent variable.
What should you do if the pH is the control variable? (1)
Use a buffer solution in the correct range for the enzyme used and as near to the optimum as possible.
What should you do if the temperature is the control variable? (1)
Use a thermostatically controlled water bath set in the correct range for the enzyme used and as near to the optimum as possible.
What should you do if the enzyme concentration is the control variable? (1)
Should be in excess is substrate concentration is the independent variable.
What should you do if the substrate concentration is the control variable? (1)
Should be in excess is enzyme concentration is the independent variable.
What is the effect of temperature on enzyme activity? (2)
As temperature rises to an optimum, increasing kinetic energy causes more collisions and more enzyme substrate complexes are formed. Above the optimum, active site shape changes lead to a fall in rate as the substrate is less likely to enter the active site.
What is the effect of pH on enzyme activity? (1)
The concentration of charged particles such as H+, affects the active site shape. Most enzymes have an optimum pH around 7, but some are different.
What is the effect of substrate concentration on enzyme activity? (1)
As more substrate is added, more active sites are occupied. When all active sites are occupied, adding more substrate does not increase the rate.
What is the effect of enzyme concentration on enzyme activity? (1)
As more enzyme is added, there are more active site to bind to the substrate. At a certain point all substrate is being acted on and adding more enzyme then does not increase the rate.
What are competitive inhibitors? (1)
Excess substrate overcomes the inhibition.
What is non-competitive inhibition? (1)
Excess substrate has no effect on inhibition (includes end product inhibition)
What does competitive inhibition do? (1)
Competitive inhibitors blocks the active site. With excess substrate substrate always occupiers the site before the inhibitor can.
What does a non-competitive inhibition do? (1)
Non-competitive inhibitor changes the shape of the active site, excess substrate has no effect.
What are allosteric enzymes? (1)
Some enzymes exist in two forms, an active form and an inactive form.
What is competitive inhibition? (1)
Inhibitor chemically resembles the substrate molecule and binds to the active site, blocking access by substrate molecules.
What happens when a competitive inhibitor is in low concentration? (1)
Increasing the concentration of the substrate eventually overcomes inhibition as substrate molecules displace inhibitor and enzyme - substrate collisions become more likely than enzyme - inhibitor collisions.
What is an examples of competitive inhibition? (1)
Oxygen competes with carbon dioxide for the active site of rubisco.
What is non-competitive inhibition? (1)
Inhibitor chemically unlike the substrate molecule, but binding to another (allosteric) sites changes the shape of the enzyme molecule including the active site.
What happens when the non-competitive inhibitor is in low concentration? (1)
Increasing the concentration of substrate can neither displace inhibitor nor prevent binding further inhibitor molecules.
What is an example of non-competitive inhibition? (1)
Alanine non competitively inhibits pyruvate kinase.
