Human Nutrition

• Nutrients in a balanced diet

  • Proteins
  • Carbohydrates
  • Fats
  • Minerals
  • Vitamins
  • Water
  • Fibre
• Scurvy


  Caused by a lack of vitamin C
• Rickets


  Caused by a lack of vitamin D
• Parts of the digestive system

  • Mouth
  • Oesophagus
  • Stomach
  • Duodenum
  • Ileum (small intestine)
  • Colon
  • Rectum (large intestine)
  • Liver
  • Gallbladder
  • Pancreas
• Digestion


  1. Ingestion

  2. Digestion

  3. Absorption

  4. Assimilation

  5. Egestion
• Physical digestion


  Breaking large pieces of food into small ones, done by the teeth and stomach
• Chemical digestion


  Breaking down large molecules of nutrients to small ones, so that they can be absorbed, done by enzymes in the mouth, stomach and small intestine
• Teeth


  • Help in physical digestion, grinding food into smaller pieces to increase its surface area, allowing faster chemical digestion
• Types of human teeth

  • Incisors
  • Canines
  • Premolars
  • Molars
• Chemical digestion of starch

  Amylase breaks down starch to simpler reducing sugars
• Chemical digestion of proteins

  Protease breaks down proteins to amino acids
• Chemical digestion of fats

  Lipase breaks down fats to fatty acids and glycerol
• HCl acid in the stomach

  Provides a low pH for enzymes to work, and also kills harmful microorganisms in the food
• Digestion of starch


  1. Amylase breaks down starch to maltose in the mouth and duodenum

  2. Maltase breaks down maltose to glucose on the surface of the villi in the small intestine
• Digestion of proteins


  1. Pepsin (protease) in the stomach requires a low pH

  2. Trypsin (protease) secreted by the pancreas requires a higher pH provided by alkaline substances in bile
• Bile


  Secreted by the liver, stored in the gallbladder, released into the duodenum, emulsifies fats to make them easier for lipase to digest
• Absorption


  1. Nutrients, including water, are absorbed into the blood from the small intestine

  2. More water is absorbed from the colon
• Villi and microvilli


  • Increase the surface area of the small intestine, which speeds up absorption