biological molecules tests

Question 1

test for glucose?

Answer 1

1) add benedicts solution to a sample of food
2) place in a water bath at 80 degrees celsius for 5 minutes
3) colour change: blue-> brick red

Question 2

test for glucose needs to be in a water bath at what temperature and for how long?

Answer 2

80 degrees celsius and 5 minutes

Question 3

if glucose is present but in a lower concentration, what colour will it be?

Answer 3

blue to green, yellow or orange

Question 4

test for starch?

Answer 4

1) add a few drops of orange iodine solution to the sample on a spotting tile
2) a blue- black colour indicates the presence of starch

Question 5

what is the test for proteins?

Answer 5

1) add 2cm3 of water to a food sample and shake
2) add an equal volume of dilute potassium hydroxide and shake
3) add 2 drops of 1% copper sulfate solution
4) if protein is present then a pale purple colour will form

Question 6

what is the test for lipids?

Answer 6

1) place the food sample in a test tube
2) add a small volume of ethanol and shake to dissolve any lipid in the alcohol
3) add an equal volume of water
4) a cloudy white colour - formed by the emulsion- will indicate the presence of lipids