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BIOLOGY - 4.2 food tests and graphs, 40 POINTS PAPER 2 + 15 POINTS FROM…
BIOLOGY - 4.2 food tests and graphs
IODINE
INITIALLY YELLOW
BLUE / BLACK -->
STARCH
2/3 DROPS
POSITIVE TEST --> STARCH POWDER
BIURET TEST
5/6 DROPS
INITIALLY BLUE
PURPLE / VIOLET / LILAC -->
PROTEIN
SEMI - QUANTITIVE TEST
BENEDICT'S TEST
WATER BATH THE EXTRACT
THERMOSTATICALLY CONTROLLED WATER BATH
ADD SAME QUANTITY AS THE EXTRACT
REDUCING SUGARS
--> GREEN < YELLOW < ORANGE < BRICK RED PRECIPITATE
SEMI-QUANTITATIVE TEST --> NOT A NUMBER BUT HOW MANY
REDUCING SUGARS
NO SUCROSE
MONOSACCARIDES
GALACTOSE
FRUCTOSE
GLUCOSE
DISACCARIDES
MALTOSE
LACTOSE
ETHANOL
CHOPPED EXTRACT IN ETHANOL (2 cm^3) AND SHAKE
ADD DISTILLED WATER (2 cm^3) AND SHAKE
WHITE CLOUDY EMULSION -->
FATS
EXTRACT IN SOLUTION
DCPIP
ADD DROPS OF EXTRACT WHILE SHAKING
(VIOLET - ACIDITY) COLORLESS -->
VITAMIC C
COUNT DROPS TILL THE END
HIGHER CONCENTRATION --> FEWER DROPS
OPPOSITE EXPERIMENT
DCPIP ADDED TO THE EXTRACT
FEWER DROPS --> FEWER VITAMIC C
FINAL RESULT --> DCPIP REMAINS BLUE
THERE IS NO MORE VITAMIC C TO REACT
TESTS
POSITIVE
TO SEE IF THE REAGENT WORKS PROPERLY
TO COMPARE THE RESULTS
NEGATIVE
ERRORS
CROSS CONTAMINATION
3 TIMES
DROPS --> SYRING PREFERABLE ON PIPETTE
COLUR
CHANGE SUBJECTIVE
COMPARE THEM WITH NEGATIVE AND POSITVE TEST (STANDARD CONTROL)
AGAINST A WHITE BACKGROUND
DECOLOURISE THE EXTRACT
SPECTROPHOTOMETER OR COLORIMETER
GRAPHS
DESCRIBE THE GENERAL TREND
GIVE STATISTICS FOR EVIDENCE
INTIAL - FINAL VALUES
EXPLAIN
USE A TABLE
GIVE MORE STATISTICS IF YOU CAN
40 POINTS PAPER 2 + 15 POINTS FROM PAPER 4 EXTENDED THEORY + 25 POINTS FROM PAPER 6