Biological molecules

Question 1

Elements present in carbohydrates

Answer 1

Carbon
Hydrogen
Oxygen

Question 2

Elements present in proteins

Answer 2

Hydrogen
Carbon
Oxygen
And 2 contain sulphur

Question 3

Elements in lipids

Answer 3

Carbon
Hydrogen
Oxygen ( but less than in carbohydrates)

Question 4

Structure of carbohydrates

Answer 4

Starch and glycogen are large, complex carbohydrates are made op of many smaller units such as glucose and maltose joined in a long chain
Polymer ( long chain)
Monomer ( singular)

Question 5

Structure of proteins

Answer 5

Long chains of amino acids

Question 6

Structure of lipids

Answer 6

Made up of one glycerol and 3 fatty acids.

Question 7

Test for starch

Answer 7

Iodine test
Iodine is orange/yellow
Add a few drops of iodine solution to the food sample and gently shake
Positive result blue-black

Question 8

Test for glucose

Answer 8

Benedict’s test
Benedict’s is blue
Add equal amounts Benedict’s solution to the food sample, add to water bath at 75°c for 5 minutes
Positive result:green (small amounts )
Brick -red ( large amounts)

Question 9

Test for proteins

Answer 9

Biuret test
Biuret is sodium hydroxide and is blueand copper sulphate
Add equal amounts Biuret solution to the food sample and shake gently.
Positive result: purple solution.

Question 10

Test for lipids

Answer 10

Ethanol test
Place 1 ml of oil into the test tube, add 2ml of water and mix, add ethanol and shake.
Positive result : A white cloudy suspension forms at the top.