Required practical 1 : Investigation into the effect of a named variable on the rate of an enzyme-controlled reaction.

Possible factors to investigate

Enzyme conc

Substrate conc

PH

Temperature

Inhibitors

Control experiment for measuring enzyme activity

Replace enzyme solution with

DISTILLED WATER OR

BOILED ENZYME SOLITION

Effect of ph investigation equipment

PH buffer

Test tube

Pipette

Kettle

Enzyme solution

Substrate solution

Beaker

Thermometer

Method for pH investigation

1) use beaker and thermometer to create your own water bath 25° and maintain water bath within 2°

2) add enzyme solution to test tube

3) add pH buffer to this test tube

4) add substrate solution to another test tube

5) Add both test tubes to water bath and after some time mix both test tubes

6) Record time taken for (positive results which shows substrate has been converted to product such as Benedict test showing starch → sugars or something)

7) repeat w diff ph buffers

Results table for pH investigation

(Not always film)

How can the results of the practical measuring enzyme activity be used to find the initial rate of reaction?

Plot your results on a graph of rate of reaction' against 'time'.

Draw a tangent at time = 0 to find the Initial rate

Outline the practical procedure used to measure the effect of temperature on enzyme activity, using trypsin and milk.

Immerse equal volumes of (enzyme) and (substrate), stored in different test tubes, in a water-bath for 5 minutes for the temperature to equilibrate.

Mix together and immediately start timing,

record the time taken for the milk to be completely hydrolysed (become colourless/ same as the control standard set up) (or other test to show enzyme working).

Test at least 5 temperatures, with at least 3 repeats at each temperature.

How to rate of reaction calculated from time running running running running

Rate of reaction = 1/time (UNLESS it makes value too small, then u can do even 100/t or 1000!)