Bio Molecules Tests

Question 1

test for proteins

Answer 1

• biurets
  1) add NaOH, (to make alkaline)
  2) add copper(II) sulphate solution
  observ: +=turns purple

Question 2

test for starch

Answer 2

• iodine
  1) add iodine
  observ: +=browny-orange to dark-blue black

Question 3

test for lipids

Answer 3

• emulsion test
  1) add ethanol and shake
  2) pour into water
  observ: +=solution turns milky

Question 4

test for reducing sugars

Answer 4

-benedicts
1)add benedict’s reagent and heat in water bath brought to boiling
observe: += form coloured precipitate,
green->yellow->orange->brick-red, higher conc sugar = further colour change

Question 5

non-reducing sugars

Answer 5

benedicts:

1) new sample, add dilute HCl, heat in water bath brought to boil
2) neutralise it with sodium hydrogen carbonate
3) carry out benedict’s test as normal
observe: +=same as reducing sugars