Paper 1

• Required Practical - Food tests

  Sugar

  • Add 10 drops of benedict's solution to 5cm³ of food sample
  • Leave for 5 minutes at 75°C
  • Positive result - a colour change from blue to brick-red

  Starch

  • Add some drops of iodine to 5cm³ of food sample
  • Positive result - a colour change from browny-orange to blue-black

  Protein

  • Add 2cm³ biuret solution to 2cm³ food sample and mix
  • Positive result - colour change from blue to purple

  Lipids

  • Add 3 drops of Sudan III stain solution to 5cm³ food sample and mix
  • Positive result - mixture separates into two layers with the top being bright red
• Drawing microscope observations


  • Sharp pencil
  • clear unbroken lines
  • no shading/colouring
  • subcellular structures in proportion
  • title and labels
  • magnification used
• Mitosis stages


  Grown and replication:

  • DNA duplicates
  • Two DNA arms form an x shape
  • Number of subcellular structures increases

  Mitosis:

  • Chromosomes in the centre and x split by cell fibres
  • Membranes form around each set of chromosomes (nucleus)
  • Cytoplasm and cell membrane splits
• Diffusion rate increases with temperature
• Enzymes and Digestion

  All made in pancreas and small intestine

  All work in small intestine

  (plus other places)

  Carbohydrase (eg. amylase):

  • Carbohydrates to sugars
  • Made in: salivary glands
  • Works in: mouth

  Protease:

  • Proteins to amino acids
  • Made in: stomach
  • Works in: stomach

  Lipase:

  • Lipids to glycerol and fatty acids
  • [no extra made in/works in]
• Digestion


  Bile:

  Made in: Gall bladder

  Works in: Small intestine

  Hydrochloric acid means too acidic. Bile is alkali

  Bile emulsifies fats - breaks down into smaller droplets
• Oxygen debt: the amount of oxygen needed to react with lactic acid to remove it from cells

  Lactic acid can be sent to the liver to turn back to glucose
• Fermentation:

  Glucose -> ethanol + Carbon Dioxide