Factors affecting enzyme activity Flashcards
What does it mean when an enzyme becomes denatured?
The active site of the enzyme has changed and will no longer bind to the substrate.
What is meant by the optimum temperature of an enzyme?
The optimum temperature of an enzyme is the temperature at which the rate of the reaction it catalyses is at its fastest.
A student is examining the rate of an enzyme-controlled reaction. she gradually heats her sample of enzyme and substrate to 37°C. As she increases the temperature, the rate of the reaction increases. Explain why this happens.
Increasing the temperature increases the kinetic energy of the molecules, which makes them move faster. This increases the likelyhood the enzyme and its substrate will collide. The energy of these collisions also increases, which makes each collision more likely to result in a reaction.
a student heats her sample of enzyme and substrate to 70’C and observes that the reaction stops. Explain why.
the rise in temperature increases the vibration of the enzyme molecules. When the temperature rises above a certain point, this causes the bonds holding the enzymes tertiary structure to break. As a result the active site changes shape and will no longer bind to the substrate/ the enzyme becomes denatured and the reaction can no longer continue.
A student conducts two experiments, examining the affect of concerntration of enzymes, on the rate of enzyme controlled reactions. She uses double the concerntration of enzyme in her second experiment, but she dosen’t see any increase in the rate of reaction. Why might this be?
The student doe snot see an increase beacsuse the amount of substrate in the reaction is a limting factor. This means there is already an excess of the enzyme in the reaction, so increasing its concerntration will have no further affect.
What is the optimum pH of the enzyme. Explain how pH can effect the rate of the enzyme-controlled reaction.
The optimum pH for the enzyme is pH 7. Above and below an enzyme’s optimum pH, the increase in H+ or OH- ions can affect the ionic and hydrogen bonds that maintain the tertiary structure of the enzyme. When these bonds break, the enzyme’s active site changes shape and becomes denatured.
What is an enzyme inhibitor?
An enzyme inhibitor is a molecule that binds to an enzyme and reduces its activity by stopping it from binding onto a substrate.
Why does increasing the concerntration of the substrate initially increase the rate of reaction.
As the concerntration of the substrate increases, the likelihood of a collision between an enzyme and a substrate increases, increasing the rate of reaction.
If no other variables are changed in a reaction, why does the rate of a reaction decrease over time?
The rate of the reaction decreases over time because the concerntration of the substrate decreases.
How does a competitive inhibitor inhibit enzyme controlled reactions?
Competitive inhibitors bind to the active site of an enzyme as they have a similar shape to the substrate. This blocks the active site and prevents the substrate from binding to the active site.
Explain how a non-competitive inhibitor inhibits enzymes.
Non-competitive inhibitors bind to the enzyme away from its active site. This causes the active site to change shape so the substrate will no longer be able to bind to it.
A student is measuring the rate of an enzyme-catalysed reaction. As she adds more substrate the rate of reaction increases until it begins to plateau. Explain why it plateaus.
As the concerntration of the substrate increases , evetually all the active sites of the enzymes become occupied with substrate and become saturated. As a result, increasing the concerntration of the substrate will will have no further affect on the rate of reaction.
A student is measuring the rate of an enzyme catalysed reaction, gradually increasing the concerntration of substrate. She repeats her experiment three times. her results are shown on the graph below.
What type of inhibitor is A? Explain your reasoning.
What type of inhibitor is B? Explain your reasoning.
Inhibitor A is a competitive inhibitor. The rate of reaction is reduced in comparison to when no inhibitor is added but still increases as the substrate concerntration increases. This is because the substrate’s chances of getting to an active site before the inhibitor increases as the substrate concerntration increases.
inhibitor B is a non-competitive inhibitor. This is because increasing the substrate concerntration has no effect on increasing the rate of reaction as enzyme activity will still be inhibited.
