Paper 6 practicals Flashcards
How to test for protein
Biuret reagant: positive result = mauve/purple … negative result = blue
How to test for fats/lipids
Emulsion test: sample + 95% ethanol into equal volume of distilled water –> positive result = milky white emulsion
How to test for starch
Iodine solution: positive result = blue/black … negative result = orange/brown
How to test for glucose (reducing sugars)
Benedict’s solution + HEAT : blue = none … green/yellow = traces … orange = moderate amount … brick-red = large amount
Effect of changing light intensity on photosynthesis in elodea
Count number of bubbles produced in one minute with different light intensities to observe changes.
How to destarch a leaf
place in the dark for at least 24 hours
How to test a leaf for starch
- Boil leaf in water for 2min (to break down cell walls and stop enzyme action in leaf) safety precaution: use water bath instead of naked flame
- Warm leaf in ethanol until leaf is colourless (to extract chlorophyll which would mask observations later) (chlorophyll dissolves in ethanol but not in water)
- Briefly dip leaf into warm water (to soften the now brittle leaf and allow penetration by iodine solution)
- Place leaf on white tile and add iodine solution
- Positive result = blue black –> can photosynthesise (negative result = orange/brown –> can’t photosynthesise)
Substance that absorbs carbon dioxide out of air
Soda lime
Substance that gives out carbon dioxide
saturated sodium hydrogen carbonate
How to compare inhaled and exhaled air using limewater
Two tubes, pipe leading into limewater of one and air in other, short side has long pipe from air, long side has short pipe from air
- Person breathes out through central tube
- In one tube the limewater will turn milky white (expired air in long tube)
- One tube limewater turns slightly white from inspired air
Factors needed for germination
water, oxygen, warmth
