Biology Required Practicals

Question 1

Microscope practical - How to prepare a slide?

Answer 1

1. Place a drop of water onto the slide
2. Using forceps, remove a thin layer of onion
3. Place the specimen on the slide gently
   4 Using a pipette add 2-3 drops of stain (iodine)
4. Slowly at a 90° angle lower the cover slip to cover he specimen

Question 2

Microscope practical - How to use a light microscope?

Answer 2

1. Carry the microscope under the base and one hand on the arm
2. Plug in and swicth on the light source
3. Clip in the prepared slide onto the stage
4. Select the lowest power objective lens first
5. Look down the eyepiece lens
6. Turn the course focus (adjustment) wheel to move the stage upwards and get a rough image.
7. Turn the fine focus wheel to get a more precise image.
8. Select the medium power objective lens and repeat steps 5-6

Question 3

Osmosis practical - what does it look like

Answer 3

• Test tube rack with a test tube.

- Potatoes in the test tube filled with sugar solution and water

Question 4

Osmosis practical - method

Answer 4

1. Use a cork borer to cut five potato cylinders of the same diameter
2. Use the knife to trim off any potato skin of each potato cylinder. Trim to the same length
3. Accurately measure the mass/length of each potato
4. Measure 10cm^3 of each concentration of sugar or salt solution and put into boiling tubes.
5. Measure 10cm^3 of distilled water into the fifth boiling tube.
6. Add one potato cylinder to each boiling tube
7. Leave them for a chosen amount of time.
8. Remove the potato cylinders from the boiling tubes and carefully blot them dry with potato towels.
9. Measure the new mass and length of each potato again.

Question 5

Osmosis practical - Formula to find the change in mass

Answer 5

(Final mass - initial mass) / inital mass x 100

Question 6

Food sample for the presence of lipids

Answer 6

1. Place a sample of the food (solution) is a test tube.
2. Add a few drops of ice cold ethanol to the solution.
3. Shake the test tube and leave for a min
4. A cloudy white layer of precipitate will appear on the top of the water if fats are present.

Question 7

Food test to find starch present

Answer 7

1. Place a small amount of food on a spotting tile.
2. Add 2-3 drops of iodine to food samlle
3. Positive result: colour change from yellow/red to blue/black

Question 8

How to find the presence of sugar?

Answer 8

1. Place a sample of food in a test tube.
2. Add 2-3 drops of benedict’s solution to the food sample
3. Heat the test tube in a warm water bath (80°C)
4. Positive result: colour change from blue to BRICK-RED

Question 9

How tp find the presence of protein

Answer 9

1. PLACE food samlle into a test tube
2. Add 2-3 biuret solution to the food sample, heat in a warm water bath
3. Colour change from pale blue to violet, protein is present.