P1- Required Practicals

Question 1

1) Microscopy

Answer 1

1. Peel off the epidermal layer of onion using forceps
2. Mount onto a microscope slide with drop of water using pipette, making sure tissue lies flat
3. Add 2 drops of iodine solution to stain the cells
4. Place cover slip on making sure no air bubbles are trapped
5. Remove any excess stain by soaking with paper towels
6. Place the slide on the stage of the microscope
7. Turn nose piece to select a low power objective
8. Set up microscope. Use coarse adjustment knob to raise stage until cover slip just touches the objective
9. Look into eyepiece, turn adjustment knob to move stage away until image focuses
10. Turn nose piece to select high power objective
11. Repeat process, look into eyepiece, turn fine adjustment knob until image focuses
12. Make labelled diagrams of the cells you see

Question 2

2) Microbiology

Answer 2

1. Spray bench with disinfectant
2. Mark 3 segments with a dot in the middle of each and your name and name of the bacteria on bottom of agar plate
3. Wash hands
4. Place different antiseptics with onto different filter paper discs
5. Lift lid of agar plate, use forceps to place each filter paper discs onto the dots
6. Tape lid onto plate securely but loosely enough for oxgen to reach bacteria
7. Place agar plate in incubator at 25degrees for 48 hours
8. Measure diameter of clear zones after. Take second measurement at 90degrees from first measurement and take a mean for diameter (don’t remove lid)
9. Record results in a table and calculate area

Question 3

3) Osmosis

Answer 3

1. Use cork borer to cut 5 potato cylinders
2. Trim cylinders to all the same length (3cm)
3. Accurately measure and record lengths and mass of each
4. Measure 10cm3 of the 1.0M sugar solution, transfer to first boiling tube and label
5. Repeat s4 other concentrations of solution and distilled water
6. Add 1 potato cylinder to each boiling tube
7. Prepare a table
8. Leave cylinders in tubes overnight in test tube rack
9. Remove cylinders, blot dry with paper towels
10. Measure length and mass of each cylinder, record measurements in a table. Calculate %change of each
11. Plot graph change in mass against conc of sugar solution
12. Plot graph change in length against conc of sugar solution

Question 4

4a) Food tests (Starch)

Answer 4

1. Put some of food sample in a test tube
2. Add a few drops of iodine solution to sample using pipette
3. If starch is present, solution turns blue/black
4. Note any colour change in a table

Question 5

4b) Food tests (Sugars)

Answer 5

1. Add equal volume of Benedict’s solution to sample in test tube
2. Place in a hot water bath for a few minutes
3. If simple sugars are present, a brick red precipitate is formed, if not the solution remains blue
4. Note any colour changes in a table

Question 6

4c) Food tests (Protein)

Answer 6

1. Add a few drops of Biuret’s reagent to sample in test tube
2. Shake solution to mix and wait a few minutes
3. If protein is present, solution goes from blue to purple
4. Note any colour changes in a table

Question 7

4d) Food tests (Lipids)

Answer 7

1. Add a few cm3 of ethanol to the food sample
2. Pour mixture into a test tube of equal volumes of distilled water
3. If lipids are present, white emulsion is formed on the surface of the mixture
4. This is called the emulsion test

Question 8

5) Enzymes

Answer 8

1. On a tile, label each well with time, add drop of iodine solution to each well
2. Add 2cm3 of each buffer solution using a syringe into each labelled test tube
3. Immerse starch, amylase solution and 2 buffer solution test tubes in water bath at 25 degrees
4. Allow few mins for temperature to equilibrate
5. Use syringe, add 2cm3 amylase into a buffer solution test tube
6. Use syringe add 2cm3 starch into same tube and start timer
7. Use glass rod, transfer a drop of the mixture to the well labelled ‘0’ on the tile
8. Repeat s6 every 30 secs, rinsing glass rod in between until iodine remains brown
9. Calculate rate of enzyme reaction using 1/time to stay brown
10. Repeat 2-8 for buffer solutions of different pH
11. Plot graph rate of enzyme reaction against pH

Question 9

6) Photosynthesis

Answer 9

1. Place test tube rack with a boiling tube in 10cm away from lamp
2. Fill tube with fixed vol of sodium hydrogen carbonate solution
3. Place cut pondweed into boiling tube with cut end at top
4. Gently push pondweed down with glass rod
5. Start stopwatch, count number of bubbles produced in 1 min
6. For each light intensity/distance, repeat twice, calculate mean
7. Record in a table
8. Repeat for 3 more distances
9. Plot graph of rate of photosynthesis against light intensity