Biomolecules: Practical 1- Food test

Apparatus

• 6 test tubes
• 1 250cm3 beaker
• 1 tripod stand and wire gauze
• 2 10cm3 measuring cylinders
• benedicts sol, iodine sol, ethanol sol, dilute sodium hydroxide, copper (11) sulphate,
• hot water supply
• distilled water
• sol1: glucose sol
• sol 2: egg albumen
• sol 3: starch suspension
• sol 4: oil
• Unknown A and B

Procedure:

Iodine test for starch

1. Add 2 cm3 of sol 3 to clean test tube, followed by a few drops of iodine sol
2. Record your observations and conclusions

Biuret's Test for Proteins

1. Add 2 cm3 of sol 2 to a clean test tube, together with 2cm3 of dilute sodium hydroxide sol. Stir to mix the contents
2. Using a pipette, add copper (ll) sulphate drop by drop, mixing the contents after the addition of each drop.
3. Record observations.

Benedict's Test for Reducing Sugar

1. Pour about 2 cm3 of sol 1 into a test tube and add ane qual volume of Benedict's sol. Shake the mixture
2. Heat the test tube in the boiling water bath for 4 minutes.
3. Record observations.

Ethanol Emulsion Test for Fats

1. Add 2 cm3 of sol D to a clean test tube together with 2 cm3 of ethanol.
2. Record your observations of the contents after shaking test tube vigorously for 1 minutes.
3. Add 2 cm3 of water to the test tube and mix.
4. Record observations.

Solution	Benedict Test		Iodine Test			Biuret’s Test			Ethanol Emulsion Test
	Observations	Conclusions		Observations	Conclusions		Observations	Conclusions		Observatons	conclusions
1	An orange precipitate was obtained	Moderate amount of reducing sugar is present		X	X		x	X		X	X
2	X	X		X	X		The mixture turned violet	Protein is present		X	X
3	X	X		The mixture turned blue black	Starch is protein		X	X		X	X
4	X	X		X	X		X	X		A white emulsion was obtained	Lipid is present
A	A brick-red precipitate is was obtained	Large amounts of reducing sugar is present		The mixture remained brown	No starch is present		The mixture remained blue	No protein is present		The mixture remains clear	No lipid is present.
B	The mixture remained blue	No reducing sugar is present		The mixtured turned blue black	Starch is present		The mixture turned violet.	Protein is present		A white precipitate	Lipid is present