RP1 - effect of named variable on rate of enzyme-controlled reaction

Question 1

caesin is a protein found in milk. trypsin is an enzyme that digests casein. when trypsin is added to milk powder, casein digested and solution goes clear. tested at 4 temperatures.
Q: explain why buffers are used

Answer 1

to resist change in pH

Question 2

caesin is a protein found in milk. trypsin is an enzyme that digests casein. when trypsin is added to milk powder, casein digested and solution goes clear. tested at 4 temperatures.
Q: the test tubes were left in the water bath for 10 mins before adding enzyme. explain why

Answer 2

so there is a known temp when the reaction takes place/to equilibrate

Question 3

caesin is a protein found in milk. trypsin is an enzyme that digests casein. when trypsin is added to milk powder, casein digested and solution goes clear. tested at 4 temperatures.
Q: describe and explain what was done to make temperatures as reliable as possible

Answer 3

• repeatedly check temperature throughout
• add cold/hot water where appropriate
• to keep temp close to required temp

Question 4

caesin is a protein found in milk. trypsin is an enzyme that digests casein. when trypsin is added to milk powder, casein digested and solution goes clear. tested at 4 temperatures.
Q: explain why 3 experiments were set up at each temp

Answer 4

• more reliable data can be calculated
• anomalies identified

Question 5

caesin is a protein found in milk. trypsin is an enzyme that digests casein. when trypsin is added to milk powder, casein digested and solution goes clear. tested at 4 temperatures.
Q: student set up controls containing milk powder, buffer but no trypsin. what would the controls show?

Answer 5

the casein digested was due to enzyme action not temp

Question 6

caesin is a protein found in milk. trypsin is an enzyme that digests casein. when trypsin is added to milk powder, casein digested and solution goes clear. tested at 4 temperatures.
Q: suggest appropriate control for this investigation

Answer 6

boiled trypsin

Question 7

caesin is a protein found in milk. trypsin is an enzyme that digests casein. when trypsin is added to milk powder, casein digested and solution goes clear. tested at 4 temperatures.
Q: it is difficult to decide when milk solution goes clear. suggest one better way of determining when it goes clear

Answer 7

use a colorimeter and time how long it takes to reach constant absorbance reading

Question 8

caesin is a protein found in milk. trypsin is an enzyme that digests casein. when trypsin is added to milk powder, casein digested and solution goes clear. tested at 4 temperatures.
Q: in this experiment temperature of water bath was controlled. suggest 2 other variables that should be controlled

Answer 8

• enzyme concentration (trypsin)
• substrate concentration (casein)
• pH

Question 9

caesin is a protein found in milk. trypsin is an enzyme that digests casein. when trypsin is added to milk powder, casein digested and solution goes clear. tested at 4 temperatures.
Q: describe how method can be changed to make it more reliable

Answer 9

carry out at least 5 repeats and find mean

Question 10

a scientist used Benedicts test to produce calibration curve of colorimeter reading against maltose concentration. describe how the scientist did this . do not include details of Benedict’s test

Answer 10

• carry out Benedict’s test on known maltose concentrations
• use colorimeter to find absorbance values
• plot calibration curve (maltose concentration = x axis and absorbance value = y axis)
• find concentration of sample from calibration curve

Question 11

how can student make sure that pH of protease solution did not change?

Answer 11

use buffer