All Required Practicals in paper 1

Question 1

Preparing a slide on a microscope

Answer 1

1) Add a drop of water to the middle of a clean slide
2) Cut an onion and separate into layers, use tweezers to peel off epidermal tissue.
3) Using the tweezers, place the tissue into the water on the slide.
4) Add a drop of iodine solution as a stain to highlight the object.
5) Place a cover slip on top without getting bubbles underneath.

Question 2

Investigate the effect if antibiotics on bacterial growth

Answer 2

1) Place paper discs soaked in different types of antibiotics on an agar plate that has even covering of bacteria.
2) The antibiotic should diffuse into the agar jelly creating an inhibition zone.
3) Use a control, a paper disc soaked in sterile water to compare.
4) Leave the plate taped shut for 48 hours at 25 degrees C
5) The more effective the bacteria, the larger the inhibition zone, measure them to compare.

Question 3

Investigating the effect of pH on enzyme activity.

Answer 3

1) Put a drop of iodine solution into every well of the spotting tile.
2) Heat water over a bunsen burner to 35 degrees C, keep temperature constant.
3) Use a syringe to add 1 cm3 of amylase solution and 1 cm3 of a buffer solution with pH 5 to a boiling tube.
4) Put the tube into the water for 5 mins.
5) Use a different syringe to add 5 cm3 of starch solution.
6) Immediately mix the contents and start the stop clock.
7) Take a fresh sample of the boiling tube using a pipette every 30 secs, and put a drop into each well. When the iodine solution remains browny orange, starch is no longer present.
8) Repeat the whole experiment using different pH buffer solutions.

Question 4

How to food test for sugars

Answer 4

1) Add 5 cm3 of sugar sample to a test tube.
2) Add some Benedict’s solution to the test tube using a pipette.
3) Place in water bath set to 75 degrees C

Question 5

How to food test for starch

Answer 5

1) Add 5cm3 of starch food sample to test tube.
2) Add few drops of iodine solution and gently shake the tube.
3) If the sample contains starch, the colour changes from brown/orange to black and black/blue.

Question 6

How to food test for proteins

Answer 6

1) Prepare 2 cm3 in a test tube.
2) Add 2 cm3 of biuret solution and gently shake
3) If protein is present, the solution will change from blue to pink or purple.

Question 7

How to food test for lipids

Answer 7

1) Add 5 cm3 of lipid sample to test tube
2) Use a pipette to add 3 drops of Sudan III stain solution and gently shake.
3) If the sample contains lipids, the mixture will separate into one red layer above a white layer.

Question 8

How to see how light intensity changes the rate of photosynthesis

Answer 8

1) Place light source at a specific distance from pondweed in water in a test tube.
2) The pondweed is left to photosynthesise for a set amount of time. The oxygen released and collected in the capillary tube.
3) The syringe is used to draw the gas bubble in the tube along the ruler and the length of the gas bubble is measured.