Biology RQs

Question 1

Microscope practical method

Answer 1

Use a dropping pipette to put a drop of water onto a glass slide.
2. Separate one of the thin layers of the onion.
3. Using a forceps peel off a thin layer of epidermal tissue from the inner surface.
4. Place this thin layer on to the drop of water that you have placed on the microscope
slide.
5. Make sure that the layer of onion cells is flat on the slide.
6. Put 2-3 drops of stain solution onto the onion tissue.
7. Carefully lower a coverslip onto the slide. Do this by:
i) placing one edge of the coverslip on the slide at a 90 degree angle and
ii) use the mounted needle to lower the other edge onto the slide.
8. Use a piece of blotting paper to soak any excess liquid on the slide.
9. Put the prepared slide on the microscope stage

Question 2

Enzymes RQ method

Answer 2

1) Label 3 test tubes ( pH, starch, amylase
2) One drop of iodine into each depression in spotting tile
3) 2cm^3 starch solution to start test tube, 2cm^3 amylase solution to allotted test tube and same with pH
4) place all test tubes in water bath and wait till all have reached 30 degrees
5) use syringe to place 2cm^3 of starch to buffered pH solution test tube
6) another syringe, add 2cm^3 amylase to pH+starch test tube
7) immediately start stop clock and leave it on throughout test
8) mix using glass rod
9) every 20 secs remove one drop of mixture and place on one depression in spotting tile ( iodine should turn blue black at first )
10) rinse rod
11) each 20 secs remove 1 drop of mixture into iodine solution, rinse glass rod each time, continue until iodine solution stops turning blue and remains orange ( no more starch )
12) repeat with other pH levels

Question 3

Food tests RQ method

Answer 3

1. Use a pestle and mortar to grind up a small sample of food.
2. Transfer the ground up food into a small beaker. Then add distilled water.
3. Stir the mixture so that some of the food dissolves in the water.
4. Filter using a funnel with filter paper to obtain as clear a solution as possible. The solution should be collected in a conical flask.
5. Half fill a test tube with some of this solution.
6. Add 10 drops of Benedict’s solution to the solution in the test tube.
7. Put hot water from a kettle in a beaker. The water should not be boiling. Put the test tube in the beaker for about five minutes.
8. Note any colour change.
   If a reducing sugar (such as glucose) is present, the solution will turn green, yellow, or
   brick-red. The colour depends on the sugar concentration.
9. Take 5 ml of the solution from the conical flask and put it into a clean test tube.
10. Add a few drops of iodine solution and note any colour change.
    If starch is present, you should see a black or blue-black colour appear.

Question 4

B6 RQ method ( Not Needed )

Answer 4

1. set up a bunsen burner burning with a safety flame
2. Use a marker to draw 4 quadrants on the underside of the jelly plate and number them
3. open the bottle of bacteria ( bacillus subtilis ) and fire it against the bunsen burner ( turn the rim of the open bottle around in the flame for a small rime )
4. Pour a medium sized drop of bacteria onto the agar jelly and use a sterylised spreader to spread the bacteria around the plate ( make sure quickly put the lid back onto the jelly plate )
5. Used steryljsed forceps to pick up a disc of antiseptic ( penicillin, streptomycin, TCP, water ) and place in the 4 quadrants of the jelly, make sire to only open the lid slighlty for each appliance of the disc. Make sire to remember what number is which antibiotic
6. Put a few strips of tape on the plate and leave for at least 48 hours for the bacteria to grow.
7. After the growth, measure the zones of inhibition for each antibiotic ( using pi x r^2 ) and determin which is the most effective.

Question 5

B1 osmosis rp

Answer 5

1. Use a cork borer to cut five potato cylinders of the same diameter.
2. Use the knife to trim off any potato skin on each potato cylinder. Then trim each potato cylinder
   so that they are all the same length
3. Accurately measure the mass (g) of each potato cylinder.
4. Accurately measure the length of each cylinder.
5. Record your measurements in a table
6. Measure 10 cm3 of each concentration of sugar or salt solution and put into boiling tubes.
   Label each boiling tube clearly.
7. Measure 10 cm3 of distilled water and put into the fifth boiling tube. Label the boiling tube. clearly with the correct 0% sucrose concentration.
8. Add one potato cylinder to each boiling tube.
9. Leave the potato cylinders in the boiling tubes for a chosen amount of time.
10. Remove the potato cylinders from the boiling tubes and carefully blot them dry with the paper towels.
11. Measure the final mass and length of each potato cylinder again. Record your measurements for each concentration in your table.