Experiments

Animal cell:

  1. Swab the inside of the cheek using a cotton bud and smear the sample onto a slide

  2. Use a mounted needle to slowly lower the coverslip down over the slide at an angle to prevent airbubbles

  3. Add a drop of methlyne blue and draw through to the other side using filter paper

  4. Place the slide in the center of the microscope and secure in place using clips. Turn the light source on, then examine at low power using the coarse focus wheel before using the fine focus wheel at high power.

  • Cover slip - protects the sample from drying out, or the lens from staining

Plant cell:

  1. Cut an onion in half using a scalpel then peel back the 2 fleshy leaves to reveal the epidermis.

  2. Use a foreceps to carefully peel off a thin layer of epidermis then use a scalpel to cut it away from the onion.

  3. Use a paintfrush to transfer one piece of tissue to a drop of water on the slide, which is secured by clips

  4. Use a mounted needle to slowly lower the coverslip down at an angle to prevent airbubbles from forming.

  5. Add a drop of iodine to the sample and draw through to the other side using tissue paper

  6. Place the slide in the center of the microscope, then secure with clips. Turn the lightsource on then use the coarse focus wheel at low power before the fine focus wheel at high power

Production of ethanol using yeast:

  1. Sterilise all equipment

  2. Add the glucose solution to the conical flask and leave to sit for 5 minutes

  3. Once cool, add a sachet of yeast and cover the solution with oil

  4. Connect the flask to a beaker using glass tubing

  5. Place the conical flask in a water bath at 30C for 24 hours or until fermentation stops

  1. Control flask; the exact same setup, but add glucose only and no yeast

Results;

a. test flask containing glucose and yeast: limewater turns from clear to milky indicating carbon dioxide. Yeast ferments releasing carbon dioxide gas.

b. control flask containing only glucose: limewater stays the same and no carbon dioxide gas as fermentation has not occurred.

To test for the presence of ethanol

  1. The Iodform test. Remove the yeast and add an equal volume of potassium iodide. Solution turns from colourless to yellow. Repeat with the same set up, solution remains colourless.

Investiagte the effect of ph on catalase:

  1. Add to the graduated cylinder

  • 5g of chopped celery

  • Washing up liquid

  • ph buffer of 4ph

  1. Add 10cm3 of hydrogen peroxide (20) into the test tube via syringe

  2. Stant cylinder and test tube in a water bath of 25C

  3. Calculate the rate of enzyme activity

  • Measure and record the foam height per minute

  1. Repeat using ph 7, 9, 11, 13

  2. Set up a control, the same set up but without any celery

Conclusion:

  • Most activity at ph9 - optimum ph level

  • ph level affects catalase activity

  • no foam at ph 4, 13 as it was denatured

  • little to no foam at ph 7, 11 as it was inactive

Investigate the effect of temperature on catalase activity

  1. To a graduated cylinder, add;

  • 5g of chopped celery

  • ph buffer 9 solution

  • detergent

  1. Add 10cm3 of hydrogen peroxide to the test tube using a syringe

  2. Add both the test tube and graduated cylinder to a water bath at 0C

  3. Calculate enzyme activity

  • Measure and record the foam height per minute

  1. Repeat using water bath at temperatures 25, 45, 60

  2. Set up a control and repeat with the same set up, without the enzyme

Conclusion;

  • Temperature effects catalase activity

  • No activity at 0C as the enzyme is denatured

  • Most activity at 25 as this is the optimum temperature

  • Little to no activity at 45

  • No activity at 60 as the enzyme is denatured

Investigate effect of heat denaturation on enzyme

  1. Boil the celery at 100C to denature it for 5 minutes

  2. Add the denatured enzyme to a graduated cylinder with ph9 and a drop of washing up liquid.

  3. Add 10cm3 of hydrogen peroxide to a test tube using a syringe

  4. Stand the graduated cylinder and test tube into a water bath of 25C. Then add hydrogen peroxide into the cylinder

  5. Measure and record the foam height per minute

  6. Set up a control using the same set up, but with an untreated, un boiled enzyme

  7. Provide optimum conditions for both the test and the control

Conclusion:

  • Test: no activity as the enzyme is denatured

  • Control: lots of activity as the enzyme is in optimum conditions