core practicals (do the p2 during half term) Flashcards
Effect of pH on enzyme activity (+ control variables and problems)
- PAPER 1 & 2
- drop of iodine solution into every well on a spotting tile (control)
- Add 3cmcubed of Amylase solution and 1cmcubed of pH 5 buffer solution to a boiling tube and place in a 35’C water bath and wait 5 minutes
- Add 3cmcubed of starch solution to the boiling tube and immediately mix the contents and start a stop watch
- Every 10 seconds put a drop into a different well of iodine solution and it should turn blue black at first
- When the iodine solution remains orange-brown, starch is no longer present
- Repeat experiment with buffer solutions with different pH values
CONTROL VARIABLES - Concentration and volume of amylase solution
PROBLEMS - Only an approximate time as it is every 10 seconds
Investigating osmosis
- PAPER 1 & 2
1) Prepare sucrose solutions of different concentrations ranging from pure water to very concentrated sucrose solution
2) Use a cork borer to cut a potato into the same sized pieces from the same potato (approx. 1cm diameter)
3) Measure the mass of each cylinder
4) Place one cylinder in each solution concentration
5) Leave them in the solution for at least 40 minutes
6) Remove them and pat them dry, weigh each group again
7) Calculate % mass change
Investigating antibiotics
- PAPER 1
1) Divide disc into 3 segments with a marker pen, and label them control, and the name of the other antibiotics
2) Add bacterial culture to the agar and spread it with a spreader
3) Sterilize forceps and add the antibiotics + filter paper control disc to each section
4) Tape lid shut, flip over disc and leave at 25’c in an incubator for 48 hours
5) Calculate the zone of inhibition
