Digestion System

• Digestion

  The process of breaking down large insoluble molecules of food into small soluble molecules that can be absorbed into the blood
• Digestive system

  The system in the body that carries out the process of digestion
• Functions of the digestive system

  • Digest large insoluble molecules to small soluble ones by using enzymes
  • Absorb small soluble molecules into the blood
• Digestion

  1. Large insoluble molecules broken down into small soluble molecules

  2. Chemical digestion (enzymatic hydrolysis)

  3. Mechanical digestion
• Ingestion

  Food enters the body
• Absorption

  Small soluble molecules taken into blood stream
• Egestion

  Undigested food passed out
• Digestive enzymes

  Enzymes that speed up the process of breaking down large insoluble molecules to small, soluble molecules
• Digestive enzymes and their functions

  • Carbohydrase (breaks down starch to glucose)
  • Protease (breaks down proteins to amino acids)
  • Lipase (breaks down fats to fatty acids and glycerol)
• Every enzyme is specific to only one food group
• Products of digestion of different food types

  • Starch -> Glucose
  • Fats -> Glycerol + Fatty acids
  • Proteins -> Amino acids
• Testing for products of digestion

  1. Protein - Biuret test

  2. Glucose - Benedict's test

  3. Starch - Iodine test
• Organs of the digestive system and their functions

  • Mouth - Starch digestion begins
  • Oesophagus - Transports food
  • Stomach - Secretes protease
  • Small intestine - Continued digestion and absorption
  • Liver - Produces and secretes bile
  • Gall bladder - Stores bile
  • Pancreas - Secretes digestive enzymes
  • Large intestine - Absorbs water
  • Anus - Egestion of waste
• Peristalsis

  The contraction of muscles in the gut wall that moves food along the digestive system
• Bile

  A fluid produced in the liver and stored in the gall bladder that emulsifies fats, increasing their surface area for enzyme action
• Absorption in the small intestine

  Small soluble food molecules diffuse into the bloodstream, facilitated by the large surface area of villi and the concentration gradient
• Visking tubing is a limited model for the gut as it lacks the folded surface area, blood flow, and muscular contractions of the real digestive system
• Balanced diet

  Eating the right amounts of the essential food groups
• Energy intake from food

  Must be balanced with energy output in exercise
• Excess energy is stored as fat, leading to obesity
• Dietary nutrients

  • Carbohydrates
  • Proteins
  • Fats
  • Vitamins
  • Minerals
  • Fibre
  • Water
• Food labelling

  Provides information on nutrients, guideline daily amounts, and food additives to help consumers make informed choices
• Investigation of energy content of foods

  1. Measure temperature increase when burning food under water

  2. Calculate energy released per gram of food
• Different foods have different energy contents that can be released by burning