RP1

Question 1

What type of test is a colorimeter?

Answer 1

Quantatitive

Question 2

What does the colorimeter measure?

Answer 2

The equipment measures the intensity of light transmitted through a sample

Question 3

What does increasing the concentrations of reducing sugar do?

Answer 3

An increased mass of precipitate

Question 4

What do suspended solids absord? (colorimeter)

Answer 4

Light, so the absorption reading increases

Question 5

How do you standardise the method?

Answer 5

· Samples should always be shaken before testing

· Zero the colorimeter before use (with a control)

· Use the same absorbance filter throughout

· Use same volume for each reading

Question 6

Explain why buffer solutions are used

Answer 6

To maintain a constant pH

Question 7

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 7

To reach temperature at which reaction will take place

Question 8

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

Answer 8

Measure temperature (several times) and add hot or cold water as appropriate;

To try to keep the temperature close to that required

USING A THERMOMETER

Question 9

Explain why you set up three experiments at each temperature

Answer 9

Enables calculation of a more reliable mean; So that outliers can be identified

Question 10

A student decided to improve this investigation by using a control experiment. At each temperature she set up a test tube containing milk powder and buffer but NOT trypsin. What would these control experiments show?

Answer 10

Controls show that the casein digested was due to the action of enzyme, not due to temperature changes

Question 11

Suggest an appropriate control for this enzyme controlled investigation

Answer 11

Boiled trypsin

Question 12

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 12

Use a colorimeter; Record time taken to reach constant value of absorbance

Question 13

Explain how the active site of an enzyme causes a high rate of reaction

Answer 13

1. Lowers activation energy;
2. Induced fit causes active site to change shape;
3. So enzyme-substrate complex causes bonds to break;