Required Practical 1

Question 1

You used a buffer in your investigation. Explain why buffer solutions are used.

Answer 1

Maintains constant pH

Question 2

You left the test tubes in the water bath for 10 minutes before you added the enzyme to the milk powder solutions. Explain why you did this.

Answer 2

To equillibrate

Question 3

Describe and explain what you did to make sure the temperatures of the water baths were as reliable as possible

Answer 3

Measure temperature of the water bath at the beginning and at the end of the reaction period
To assess the effect of any temperature changes during the reaction
Measure the temperature several times and add hot or cold water as appropriate

Question 4

Explain why you set up 3 experiments at each temperature

Answer 4

Enables calculation of a more reliable mean

So that anomalous data can be identified

Question 5

Suggest a more appropriate control for this enzyme controlled investigation

Answer 5

Boiled trypsin

Question 6

The student concluded that the optimum temperature for the enzyme was 40 degrees. Evaluate the conclusion

Answer 6

Conclusion is not valid as 40 degrees was the only temperature that was investigated

Question 7

It is difficult to decide when the solution of milk powder goes clear. Suggest one better way of determining when the solution of milk powder goes clear

Answer 7

Use a colorimeter

Record time taken to reach set value of transmission/absorbance

Question 8

In this experiment you controlled the rate of temperature of the water bath. List two other variables that you controlled in this investigation

Answer 8

Concentration of enzyme
Concentration of substrate
pH

Question 9

Describe how you can change the method to make it more reliable

Answer 9

Carry out at least 5 repeats and calculate a mean

Question 10

Describe the induced fit model of an enzyme action

Answer 10

(Before reaction) the active site not complementary to the substrate
Shape of active site changes as substrate binds
This is due to stressing and distorting bonds

Question 11

The scientist used quantitative Benedict’s Tests to produce a calibration surge of colorimeter reading against concentration of maltose
Describe how the scientist would have produced the calibration curve and used it to obtain the results in the graph

Answer 11

Make maltose solutions of different concentrations (and carry Benedict’s test on each)
Use colorimeter to measure colorimeter value of each solution and plot calibration curve
Find concentration of sample from calibration curve

Question 12

How should the students make sure that the pH of the protease solution did not change

Answer 12

Use buffer

Test pH at intervals

Question 13

Suggest two variables that the biochemist controlled when investigating effect of temperature on the rate of breakdown of a protein by the protease

Answer 13

Initial substrate concentration.
Enzyme concentration
pH