digestion

• what is the purpose of digestion?

  Break down large insoluble molecules in the digestive system into small soluble molecules that can be absorbed into the blood and carried to cells
• Components of a balanced diet

  • Proteins - Build bodies
  • Carbohydrates - for energy
  • Fats - provide energy
  • Minerals - iron- for haemoglobin in blood
  • Vitamins - vit C- maintains healthy tissues
  • Fibre - provides bulk
  • Water- essential for body processes and functions
• Excess amounts of any diet components can cause health problems
• Health problems from excess diet components

  • Excess high energy foods will be stored as fat leading to obesity
  • Excess sugar can lead to type II diabetes, tooth decay and obesity
  • Excess fat can lead to obesity, heart disease and circulatory disease
  • Excess salt can lead to high blood pressure
• Carbohydrates

  Broken down into glucose
• Proteins

  Broken down into amino acids
• Lipids (fats)

  Broken down into glycerol and fatty acids
• Digestion of food


  1. Food

  2. Broken down by enzymes

  3. Enzymes produced by mouth, pancreas and small intestine
• Food tests


  • Starch - Iodine (brown to blue/black)
  • Glucose - Benedict's (blue to brick red)
  • Protein - Biuret (blue to violet)
• Energy intake from food


  Excess energy stored as fat
• Energy output in exercise


  Energy intake from food
• Small intestine


  • Absorption of digested food molecules
  • Villi increase surface area for diffusion of soluble food into blood
  • Good blood supply, removing absorbed food to maintain a diffusion gradient