Paper 1 Pags Flashcards
Test for starch
1) Add iodine
2) If goes blue-black = positive, is stays browny-orange = negative
Test for lipids
1) Shake with ethanol for 1 min until dissolved
2) poor solution into water
3) lipids present = milky emulsion
Test for proteins
BIURET TEST
1) Add few drops sodium hydroxide to solution to make alkaline
2) Add copper(||) sulfate
3) positive= turns purple, negative = stays blue
Test for reducing sugars (simple sugars e.g. glucose)
1) Add Benedict’s Reagent (blue)
2) Heat in waterbath - 75°
3) coloured precipitate=positive ->blue to yellow to red, further colour change = higher conc. of sugar
Test for non-reducing sugars (e.g. sucrose)
1) Add dilute hydrochloride acid
2) Heat in waterbath- 75°
3) Add sodium hydrogen-carbonate + carry out Benedicts reagent test
4) coloured precipitate= positive, of still blue, no sugars contained at all
Test for respiration
Germinating beans produce CO2 which turns hydrogen-carbonate indicator red -> yellow if present
Test for osmosis
Potatoes indifferent sucrose solutions of different concentrations change size/length/mass
Test for enzyme activity - how fast a product appears
1) Add set amount of hydrogen peroxide to boiling tube
2) tube in water bath - 10°
3) set up apparatus
4) Add catalyse (potato) to hydrogen peroxide + attach bung quick
5) record amount of oxygen produce in 1st min
6) repeat X3 + find mean
Test for enzyme activity- how fats substrate disappears
1) set up apparatus
2) put drop of iodine in each well
3) every 10s, drop sample of mixture into well with pipette
4) once iodine remains browny/orange, record total time taken- starch no longe represent
5) repeat with different temps to see how temp affects time taken for starch to break down
Colorimeter= electrical equipment to measure strength of coloured solution- not just human judgement - improves accuracy
