Biological molecules

Question 1

List the chemical elements that make up carbohydrates

Answer 1

Carbon
Hydrogen
Oxygen

Question 2

List the chemical elements that make up fats and oils?

Answer 2

Carbon
Hydrogen
Oxygen

Question 3

List the chemical elements that make up proteins

Answer 3

Carbon
Hydrogen
Oxygen
Nitrogen

Question 4

What to simple sugars form?

Answer 4

Starch
Glycogen
Cellulose

Question 5

What do fatty acids and glycerol form?

Answer 5

Fats and oils

Question 6

What do amino acids form?

Answer 6

Proteins

Question 7

Test for starch

Answer 7

Add a few drops of iodine solution (+ve result = blue-black colour, -ve result = remains brown)

Question 8

Test for Reducing sugars

Answer 8

Add Benedict’s reagent, then the mixture is heated in a water bath for 2 to 3 minutes (70°C). (+ve result = brick-red precipitate, -ve result = remains blue)

Question 9

Test for proteins

Answer 9

Add a few drops of Biuret reagent, +ve result = purple/lilac colour

Question 10

Test for fats

Answer 10

Ethanol Emulsion test; ethanol is added to the mixture, and this is poured into a test tube with an equal amount of distilled water, then is shaken, +ve result = milky-white emulsion

Question 11

Test for Vitamin C

Answer 11

Decolourisation of DCPIP shows that a vitamin C is probably present

Question 12

Describe the structure of a DNA molecule?

Answer 12

two strands coiled together to form a double helix
each strand contains chemicals called bases
bonds between pairs of bases hold the strands together
the bases always pair up in the same way:
A with T, and C with G