RP1- investigation into the effect of a named variable on the rate of an enzyme controlled reaction

Question 1

what is an important thing to remember in this practical?

Answer 1

keep all other variables constant so that they do not influence the results

Question 2

what is step 1 of this practical?

Answer 2

1) take 3 test tubes
2) place 2cm3 of trypsin and 2cm3 of pH buffer to each
3) place 5cm3 of milk into each
4) place this in a room temp water bath and leave for 5 mins to equilibrate

Question 3

what is step 2 of this practical? (6)

Answer 3

1) take test tubes out
2) place rubber bung over test tube
3) set timer
4) invert several times to mix solution
5) record the time when the milk goes clear
6) repeat for 30, 40, 50 and 60 degrees C

Question 4

what is step 3 of this practical? (3)

Answer 4

1) draw a table to record all 3 timings for each temperature
2) calculate mean excluding any anomalies
3) calculate rate of reaction by doing 1/time

Question 5

what is step 4 of this practical? (2)

Answer 5

1) draw a graph for effect of temperature on trypsin
2) rate of reaction on y axis, temperature on x axis

Question 6

when should you join up the lines dot to dot with a ruler or draw a curve of best fit?

Answer 6

line- not enough data points/ intermediates to accurately predict pattern
curve- enough data points to accurately predict pattern

Question 7

what are the limitations to this practical? (3)

Answer 7

1) end point is subjective which leads to inaccurate ‘time taken’ measurements
2) not enough intermediate temperature values were tested to accurately identify optimum temperature
3) range of tested temperatures was not wide enough as the point at which trypsin denatures was not identified (test beyond 60 degrees)

Question 8

what is important to remember when being asked about limitations to experiments?

Answer 8

critique the method not the experimenter, always assume they have done everything correctly.