B 3.3 The chemistry of food

Question 1

1) a. Explain what a protein is

Answer 1

molecule made up of long chains of amino acids

Question 2

1) b. state how proteins are used in the body

Answer 2

structural components
hormones
antibodies
enzymes (catalysts)

Question 3

2 Describe the main similarities and differences between the tree main groups of chemicals (carbohydrates, protein. and lipids) in the body

Answer 3

similarities:
• vital components of a balanced diet
• contain carbon, hydrogen, and oxygen
• large molecules made up of smaller molecules joined together
differences:
• carbohydrates made up of sugar units
• lipids made up of fatty acids and glycerol
• proteins made up of long chains of amino acids
• lipids insoluble in water
• proteins contain nitrogen

Question 4

3 describe how you would test a food sample to see if it contains
a starch
b lipids

Answer 4

3 a) iodine test
yellow‑red iodine solution turns blue‑black if starch present

3 b) ethanol test
ethanol added to solution gives cloudy white layer if lipid present

Question 5

4 Explain why lipids can be either fats or oils

Answer 5

Lipids are made up of three molecules of fatty acids joined to a
molecule of glycerol.
Different combination of fatty acids
determines whether lipid is solid (fat) or liquid (oil)

Question 6

5 Explain how simple sugars are related to complex carbohydrates

Answer 6

Complex carbohydrates are made up of long chains of simple sugars
joined together.
Simple sugars are basic units of complex carbohydrates.