2 - HUMAN NUTRITION 

Biological molecules 

Carbohydrates - 

• Made up of simple sugars 
• Contain carbon, hydrogen and oxygen 
• Starch and glycogen are large, complex carbohydrates - made up of many smaller units (eg: glucose or maltose molecules) joined in a long chain 

Proteins - 

• Made up of long chains of amino acids 
• Contain carbon, nitrogen, hydrogen and oxygen 

Lipids - 

• Fats and oils 
• Made up of fatty acids and glycerol 
• Contain carbon, hydrogen and oxygen 

Testing for glucose (Benedict's reagent) - 

• Add Benedict's reagent (blue) to a sample (an excess) 
• Heat - do not boil 
• Positive = coloured precipitate (blue-green-yellow-orange-brick red) 
• The higher the concentration, the further the colour change goes - can compare 

Testing for starch (iodine test) - 

• Add iodine solution (iodine dissolved in potassium iodide solution - brown/orange) 
• Present = blue/black 
• No starch = stays brown/orange