EASY
AS and A Level
IMPORTANT
Earn 100

Discuss what properties of proteins might make them suitable to act as catalysts in living cells. 

Important Questions on Enzymes

MEDIUM
AS and A Level
IMPORTANT
Biology for Cambridge International AS & A Level coursebook 2nd Edition Digital Access>Chapter 3 - Enzymes>Question>Q 1

A student investigated the effect of several different catalysts on the rate of decomposition of hydrogen peroxide to water and oxygen. The speed of the reaction was judged by how 'fizzy' or frothy the contents of the tube became when the catalyst was added (oxygen is a product of the reaction and forms bubbles). The student used iron filings and manganese dioxide as inorganic catalysts. They also used a commercial preparation of the enzyme catalase and pieces of liver and pieces of potato tuber, both of which contain catalase. Catalase catalyses the decomposition of hydrogen peroxide.

Results showed: • catalase, liver and potato were much more efficient than the inorganic catalysts • pure catalase was more efficient than the liver and potato • liver was more efficient than potato • ground-up liver was more efficient than pieces of liver. Try to explain the student's results. 

MEDIUM
AS and A Level
IMPORTANT
Biology for Cambridge International AS & A Level coursebook 2nd Edition Digital Access>Chapter 3 - Enzymes>Question>Q 2

Why is it better to calculate the initial rate of reaction from a curve such as the one in. In given figure how much oxygen is given off in 30 seconds? 

Question Image

MEDIUM
AS and A Level
IMPORTANT
Biology for Cambridge International AS & A Level coursebook 2nd Edition Digital Access>Chapter 3 - Enzymes>Question>Q 3
 In the breakdown of starch by amylase, if you were to plot the amount of starch remaining against time, draw the curve you would expect to obtain. 
MEDIUM
AS and A Level
IMPORTANT
Biology for Cambridge International AS & A Level coursebook 2nd Edition Digital Access>Chapter 3 - Enzymes>Question>Q 3
In the breakdown of starch by amylase, if you were to plot the amount of starch remaining against time, draw the curve you would expect to obtain. How could you use this curve to calculate the initial reaction rate? 
MEDIUM
AS and A Level
IMPORTANT
Biology for Cambridge International AS & A Level coursebook 2nd Edition Digital Access>Chapter 3 - Enzymes>Question>Q 4
How could you carry out an experiment to determine the effect of temperature on the rate of breakdown of hydrogen peroxide by catalase? 
MEDIUM
AS and A Level
IMPORTANT
Biology for Cambridge International AS & A Level coursebook 2nd Edition Digital Access>Chapter 3 - Enzymes>Question>Q 6
Trypsin is a protease secreted in pancreatic juice, which acts in the duodenum. If you add trypsin to a suspension of milk powder in water, the enzyme digests the protein in the milk, so that the suspension becomes clear. How could you carry out an investigation into the effect of pH on the rate of activity of trypsin? (A suspension of 4g of milk powder in 100cm' of water will become clear in a few minutes if an equal volume of a 0.5% trypsin solution is added to it.) 
MEDIUM
AS and A Level
IMPORTANT
Biology for Cambridge International AS & A Level coursebook 2nd Edition Digital Access>Chapter 3 - Enzymes>Question>Q 7

Sketch the shape that would be in the given graph, if excess hydrogen peroxide were not available. (Celery extract contains catalase enzyme).

Question Image

MEDIUM
AS and A Level
IMPORTANT
Biology for Cambridge International AS & A Level coursebook 2nd Edition Digital Access>Chapter 3 - Enzymes>Question>Q 8
For each substrate concentration tested, the rate should be measured as soon as possible. Explain why.