Mandatory Experiments

To Prepare and Examine a Plant Cell:

Procedure:

Preparing the Slide

1. Using a knife, cut one segment of an onion and peel away a small layer of cells using forceps.

2. Place the layer of cells on a slide and put a drop of iodine to dye the cells to improve visibilty.

3. Place a coverslip to protect the cells and prevent them drying out by placing it at 45^o angle above the slide and gently lowering it with either a mounted needle or forceps to prevent air bubbles.

Examining the Specimen

1. Place the slide onto the stage of the microscope and secure it with the stage clips.

2. View the slide with the lowest power objective lens first, to know where to focus on with the high power lenses.

3. Ensuring that the cells are in your field of view, go to the higher power objective lens to see it in greater detail.

4. Then use the high power objective lens to see it in full detail. (Be careful as the high power objective lens is close to the slide so it may damage it if mishandled.)

Diagram:

To Prepare and Examine an Animal Cell:

Procedure:

Preparing the Slide

1. Use a cotton swab to swab your cheeks to collect cheek cells.

2. Smear the cells onto the slide.

3. Place methylene blue to dye the cells to improve visibilty.

4. Place a coverslip to protect the cells and prevent them drying out by placing it at 45^o angle above the slide and gently lowering it with either a mounted needle or forceps to prevent air bubbles.

Examining the Specimen

1. Place the slide onto the stage of the microscope and secure it with the stage clips.

2. View the slide with the lowest power objective lens first, to know where to focus on with the high power lenses.

3. Ensuring that the cells are in your field of view, go to the higher power objective lens to see it in greater detail.

4. Then use the high power objective lens to see it in full detail. (Be careful as the high power objective lens is close to the slide so it may damage it if mishandled.)

Diagram:

To Demonstrate Osmosis:

Procedure:

1. Soak two pieces of visking tubing of the same length to soften and make them pliable.

2. Tie a knot at one end of both of the tubes.

3. Dissolve a large amount of sucrose in warm water in a beaker to form a concentrated sucrose solution.

4. Fill one of the tubes with a measured amount of distilled water.

5. Fill the second tube with the exact same amount of sucrose solution as the distilled water.

6. Dry each tube and note its turgidity and record its mass.

7. Place each tube in beakers of distilled water of identical amounts.

8. Leave the tubes for 30 minutes.

9. Remove the bags, dry them and note their turgidity and record their mass.

10. Record the results of the mass at the start, the final mass, and the change in turgidity.

Diagram:

To Test for a Reducing Sugar:

Procedure:

1. Label two test tubes A and B.

2. Place glucose into tube A.

3. Place an equal amount of water in tube B.

4. Add the same volume of glucose and water of Benedict’s solution to each test tube.

5. Place the test tubes in a water bath at 80-100OC for 5-10 minutes.

6. Swirl the test tubes and note any colour changes.

7. Record results in table.

Diagram:

To Test for Starch:

Procedure:

1. Label test tubes A and B.

2. Place starch solution into tube A.

3. Place an equal amount of water in tube B.

4. Add 2-3 drops of iodine solution to both tubes.

5. Swirl the tubes and note any colour change.

6. Record results in table.

Diagram:

To Test for Protein:

Procedure:

1. Label test tubes A and B.

2. Place milk into tube A.

3. Place an equal amount of water in tube B.

4. Place an equal amount of biuret solution into each test tube.

5. Swirl the tubes and note any colour change.

6. Record results in table.

Diagram:

To Investigate Effect of pH on Enzyme Activity

Procedure:

1. Blend three stalks of celery using a hand blender and add 100cm³ of distilled water.

2. Filter this solution into a 250cm³ beaker using coffee filter paper.

3. Place this solution in a water bath at 25^oC.

4. Place 10cm³ of this catalase solution into a 100cm³ graduated cylinder and place in the water bath.

5. Add 10cm³ pH 4 buffer solution to the graduated cylinder.

6. Using a dropper, add one drop of washing-up liquid.

7. Add 5cm³ of hydrogen peroxide into a test tube and place in the water bath.

8. Leave both solutions until they have reached 25^oC.

9. Add the hydrogen peroxide to the cylinder.

10. Swirl the cylinder carefully.

11. Start the stopwatch.

12. Note the volume of foam after 2 minutes.

13. Repeat using buffers 7,10, 13.

14. Draw a graph of the results showing volume of foam against pH.

Diagram:

To Investigate Effect of Temperature on Enzyme Activity

Procedure:

1. Blend three stalks of celery using a hand blender and add 100cm³ of distilled water.

2. Filter this solution into a 250cm³ beaker using coffee filter paper.

3. Place 10cm³ of this catalase solution into a 100cm³ graduated cylinder and place in the ice bath at 0^oC.

4. Add 10cm³ of pH buffer 9 solution to the graduated cylinder.

5. Using a dropper, add one drop of washing-up liquid.

6. Add 5cm³ of hydrogen peroxide into a test tube and place in the ice bath.

7. Leave both solutions until they have reached 0^oC.

8. Add the hydrogen peroxide to the cylinder.

9. Swirl the cylinder carefully.

10. Start the stopwatch.

11. Note the volume of foam produced after 2 minutes.

12. Repeat the steps at 4 other temperatures.

13. Draw a graph of the results showing volume of foam against temperature.

Diagram:

To Prepare an Enzyme Immobilisation and Examine its Application

Procedure:

Preparation

1. Add 0.4g of sodium alginate to 10cm³ of distilled water in a 100cm³ beaker.

2. Add 2g of yeast to 10cm³ of distilled water in a seperate 100cm³ beaker.

3. Add 1.5g of calcium chloride to 100cm³ of distilled warer in a 250cm³ beaker.

4. Thoroughly mix the yeast and sodium alginate solutions.

5. Place 10cm³ of this mixture in a syringe.

6. Slowly, 1cm³ at a time, add this solution to the calcium chloride solution.

7. Beads of the immobilised yeast which conatain enzyme will form in the calcium alginate gel.

8. Allow the beads to harden for 15 minutes.

9. Filter the beads and rinse with distilled water.

Application

1. Prepare 2g of yeast in 10cm³ of distilled water.

2. Pour solution into a seperating funnel and label.

3. Place a suitbale filter in this funnel to prevent beads from clogging exit hole.

4. Place 50cm³ of prepared sucrose solution into each of the seperating funnels.

5. Open the taps of the seperating funnels and release the enzyme solutions into separate beakers.

6. Using glucose testing strips, test both solutions immediately for the presence of glucose.

7. Note the cloudiness of the solution.

8. Repeat every 30 seconds recording results until glucose is detected.

Diagram: