1: BIOLOGICAL MOLECULES - RP 1

Question 1

RP1: Investigation into the effect of a named variable (temp) on the rate of an enzyme-controlled reaction - method

Answer 1

1. Using a marker pen write an ‘X’ on the glass halfway down one side of each of three test tubes.
2. Add 10 cm3 of the solution of milk powder to each of these three test tubes.
3. Add 2 cm3 of trypsin solution to 2 cm3 of pH 7 buffer in another set of three test tubes.
4. Stand the three test tubes containing the solution of milk powder and the three test tubes containing trypsin and buffer in a water bath at 20 °C.
5. Leave all six tubes in the water bath for 10 minutes.
6. Add the trypsin and buffer solution from one test tube to the solution of milk powder in another test tube and mix thoroughly.
7. Start timer immediately
8. Time how long it takes for the milk to go clear. Do this by measuring the time taken to first see the ‘X’ through the solution.
9. Record the time
10. Repeat steps 6, 7, 8 and 9 for the other test tubes
11. Using the same method, find out how long it takes the trypsin to digest the protein in the solution of milk powder at 30 °C, 40 °C, 50 °C, 60 °C.
12. Record your data in a suitable table.
13. Process your data and draw a graph of your processed data.

Question 2

RP1: Investigation into the effect of a named variable (temp) on the rate of an enzyme-controlled reaction - variables

Answer 2

• IV: temp
• DV: time taken to see X through the solution
• CVs: pH, volume of milk powder solution, conc. of milk powder solution, volume of trypsin, conc. of trypsin, volume of buffer solution

Question 3

What is a t-test?

Answer 3

a test used to compare means to see if there’s a significant difference between 2 means

Question 4

What is a null hypothesis?

Answer 4

there is no significant difference between mean 1 and mean 2

Question 5

How do you carry out a t-test in excel?

Answer 5

• input data
• use formula to calculate mean
• use formula to carry out t-test (2 tailed, paired)
• find degrees of freedom (n (no. of repeats) - 1)
• find critical value on critical value table
• compare t-test statistic to critical values table (p value <= 0.05)
  (if t-test statistic is greater than value on critical values table, the probability that the difference is due to chance is less than 5%)