Effects of Temperature & pH (Cambridge O Level Biology)

Which graph in the image below shows the correct effect of temperature on the activity of an enzyme?

The pH of an enzyme controlled reaction is decreased by a pH of 2. 

How does this affect the rate of the reaction?

Temperature affects the rate of all enzyme-controlled reactions, as shown in the graph below.

Which row correctly describes what is happening at the points on the graph?

	X	Y
A	the enzyme has been denatured	the rate of reaction is decreasing
B	the rate of reaction is increasing	the enzyme is becoming denatured
C	the reaction is taking less time	the rate of reaction is increasing
D	the rate of reaction is decreasing	the enzyme is becoming denatured

A student decided to investigate the effect of pH on the activity of the enzyme lipase.

Five different test tubes are set up. Each test tube contains a mixture of the enzyme lipase and its substrate, a lipid.

Which condition should not be kept the same in each of the five test tubes?

Which of the following correctly describes the effect of increasing temperature from 15°C to 30°C on an enzyme-controlled reaction?

	kinetic energy of enzymes and substrates	frequency of effective collisions	shape of active site
A	no change	decreases	denatured
B	increases	increases	denatured
C	increases	increases	no change
D	decreases	no change	no change

Liver cells produce an enzyme called catalase which breaks down toxic hydrogen peroxide into water and oxygen.

A student set up an experiment where cubes of cows' liver in a test tube were incubated with hydrogen peroxide at different temperatures.

The student counted the number of bubbles of oxygen released per minute at each temperature.

Their results are shown in the table below:

temperature / oC	10	20	30	40	50
number of bubbles / minute	35	68	79	63	5

The results suggest that the optimum temperature for catalase is between which two values?

Starch is digested by the enzyme amylase. Four identical mixtures of starch and amylase were kept at different temperatures.

The graph below shows the time taken for the starch to be digested at each temperature.

At which temperature is the rate of reaction highest?