Enzymes Flashcards
What is an enzyme?
A biological catalyst which increases the rate of reaction without being used up itself in the reaction.
How can temperature change affect enzyme function?
As temperature increases, the enzyme and substrate have more kinetic energy resulting in more successful collisions per unit time.
What is the lock and key theory of enzymes?
The substrate and enzyme collide.
The substrate binds to the active site of the enzyme.
This forms an enzyme substrate complex.
Binding to the active site strains the chemical bonds in the substrate and so the reaction occurs by an alternative pathway with a lower activation energy.
Once the reaction has occurred the products do not fit the active site’s shape as well as the substrate did, so is released.
The enzyme molecule is free to catalyse the next reaction.
How does temperature change the shape of the active site?
Above the optimum temperature, the heat breaks the forced holdings the proteins in the correct shape. The shape of the enzyme therefor changes, this means the active site changes shape so that it is not longer complementary to the substrate. The substrate can not bind and the reaction can not occur. The enzyme has been denatured.
What 3 substances and how much are used to investigate the change from temperature on enzymes?
10cm^3 of 10% starch suspension.
5cm^3 of 5% amylase.
1 drop at a time of iodine solution (to add to 1 drop of mixture in a spotting tile after each minute of being heated in a waterbath.
What substances and how much are used to investigate the change from pH on enzymes?
10 potato discs of 1cm thick (contains enzyme catalase).
20cm^3 hydrogen peroxide.
Measuring amount of oxygen gas produced.
pH is altered by adding different volumes of a weak alkali (eg sodium carbonate) or a weak acid (ethanoic acid) and using universal indicator paper to determine pH of solution each time.
How does pH affect enzyme activity?
Most enzymes work best at neutral ph (7) as this is the pH inside most cells.
If the pH of the environment changes, it can affect the shape of the active site so that it is no longer complementary to the substrate. The enzyme is denatured and the reaction can no longer occur.
