REQUIRED PRACTICAL 1: Enzyme-controlled Reaction

Question 1

What was the title of the experiment

Answer 1

The effect of temperature on the rate of the reaction catalysed by trypsin

Question 2

What is casein

Answer 2

• a protein found in milk
• it was the substrate for the enzyme trypsin

Question 3

What is trypsin

Answer 3

The enzyme that digests casein

Question 4

What happens when trypsin is added to a dilute solution of milk powder

Answer 4

The casein is digested and the solution —> clear

Question 5

What were the safety precautions

Answer 5

• take care with glassware —> risk of cuts
  —> therefore don’t handle glassware with wet hands; use a test tube rack
• Ensure hot water bath doesn’t exceed 60’C —> lid may be hot and steam may be ejected

Question 6

What was the method

Answer 6

1. Add 10cm3 of milk powder solution to each 5 test tubes
2. Add 2cm3 of trypsin solution to 2cm3 of pH 7 buffer in another test tube
3. Add all the separate test tubes into the water bath with the given temp —> for 10 mins (while waiting = draw results table)
4. Add the trypsin and buffer solution to the solution of milk powder, mix thoroughly
5. Put back into given hot water bath for 4 mins
6. While you wait, chose a suitable filter for and calibrate the colorimeter —> blue light and absorbance
7. After 4 mins —> pour contents into a cuvettte and measure absorbance (arbitrary units) immediately and record results
8. Repeat steps 4, 5, 6 , 7 for the other temps
9. The higher the absorbance reading —> the more casein has been hydrolysed
10. Write data in spreadsheet on excel, create a graph of your processed data —> print into book

Question 7

What’s the IV

Answer 7

Temp (‘C)

Question 8

What’s the DV

Answer 8

Absorbance (arbitrary units)

Question 9

What is the CV

Answer 9

Time spent in water bath

Question 10

What was the uncertainty in the temp reading

Answer 10

+/- 0.5

Question 11

Why were the tubes put into the water bath for 10 mins

Answer 11

Give time to equilibrate and so both tubes are same temp when mixed

Question 12

Describe how you calibrated the colorimeter

Answer 12

• put distilled water in cuvette in colorimeter
• set to blue light and switch transmission to absorbance
• then press CAL (should be 0)

Question 13

How were random errors reduced in the method of this experiment?

Answer 13

• having multiple repeats
• so we can identify anomalous results, where a random error must’ve occurred

Question 14

When should anomalies be ignored or excluded

Answer 14

Ignored when calculating the mean

Question 15

What were the results from the experiment

Answer 15

0’C = 1.405 (arbitrary units)
20’C = 1.243 (arbitrary units)
40’C = 0.323 (arbitrary units)
50’C = 1.150 (arbitrary units)
60’C = 1.194 (arbitrary units)