CORE PRACTICAL 1 Flashcards
What is core practical 1? (1)
to investigate a factor affecting the initial rate of an enzyme-controlled reaction.
what are the ways you can measure the rate of this reaction? (2)
-the amount of substrate that has disappeared from a reaction mixture in a given period of time.
-the amount of product that has accumulated from the reaction mixture in a given period of time.
what is the first step of this practical? (2)
Plan how you will dilute the 1% trypsin stock
solution with distilled water to produce additional
test solutions of 0.2%, 0.4%, 0.6% and 0.8%. Aim
to produce 10 cm3 of each concentration. Once
checked, make up the solutions as planned.
what is the second step of this practical? (2)
Place 2 cm3 of trypsin solution and 2 cm3 of
distilled water into a cuvette. Use this as a
reference cuvette to set the colorimeter
absorbance to zero.
what is the third step of this practical? (1)
Measure 2 cm3 of milk suspension into a second
cuvette.
what is the fourth step of this practical? (2)
Add 2 cm3 of trypsin solution to the milk in the
cuvette. Working quickly, mix and place the
solution into the colorimeter and start the stop
clock.
what is the fifth step of this practical? (1)
Measure absorbance immediately and then at 15
second intervals (or more frequently if recording
electronically) for 5 minutes, or until there is little
change in absorbance.
what is the sixth step of this practical? (1)
Rinse the cuvette with distilled water and repeat
for each concentration.
what are the independent variable of this experiment? (1)
trypsin concentration
why must comparisons be made at the start of the reaction? (2)
Because the reaction is rapid and the milk (substrate) concentration quickly declines. The rate slows as the substrate is used up. Comparisons can only be made at the start of the reaction where controlled variables such as substrate concentration are the same for all levels of the independent variable.
