AQA GCSE Biology Trilogy: Food Tests

Carbohydrates consist of…

• Carbon

• Hydrogen

• Oxygen

Lipids consist of…

• Carbon

• Hydrogen

• Oxygen

Proteins consist of…

• Carbon

• Hydrogen

• Oxygen

• Nitrogen

What are complex carbohydrates made of?

Long chains of simple single units

What is cellulose used for?

Cellulose is used for support in plants

Fats and oils are classed as…

Lipids

Which is the most efficient energy store?

Lipids

Are lipids soluble in water?

No

Which of these statements is true about lipids?

\
a. Made up of 3 molecules of glucose joined to 1 molecule of fatty acid

b. Made up of 3 molecules of fatty acids joined to 1 molecule of glycerol

c. Made up of 3 molecules of glycerol joined to 1 molecule of fatty acid

b. Made up of 3 molecules of fatty acids joined to 1 molecule of glucose

b. Made up of 3 molecules of fatty acids joined to 1 molecule of glycerol

What decided whether a lipid is a solid or a liquid?

Fatty acids

What are proteins used for?

• Building cells

• Building tissues

How much of the body is protein?

15 - 16%

What foods consist of high protein levels?

• Meat

• Fish

• Pulses

• Cheese

What consists of long chains of amino acids?

Proteins

What are protein bonds sensitive to?

• pH

• Temperature

Name the 2 tests for carbohydrates

• Iodine test for starch

• Benedict’s solution test for sugars

Describe the colour change of iodine in the presence of starch

Yellow / red iodine turns blue / black

Describe the colour change of iodine in the presence of proteins

No change

Describe the colour change of iodine in the presence of lipids

No change

Describe the colour change of Benedict’s solution in the presence of sugars

Blue Benedict’s solution turns brick red (when heated)

Describe the colour change of Benedict’s solution in the presence of lipids

No change

Describe the colour change of Benedict’s solution in the presence of proteins

No change

Name the solution used in testing for the presence of lipids

Ethanol

Describe the colour change of ethanol in the presence of lipids

Colourless ethanol turns cloudy white

Describe the colour change of ethanol in the presence of sugars

No change

Describe the colour change of ethanol in the presence of proteins

No change

Name the solution used in testing for the presence of proteins

Biuret reagent

Describe the colour change of Biuret reagent in the presence of proteins

Blue Biuret solution turns purple

Describe the colour change of Biuret reagent in the presence of lipids

No change

Describe the colour change of Biuret reagent in the presence of starch

No change