Food and Digestion

• Enzymes


  Break down large molecules (food) into smaller molecules. Enzymes are mainly involved in everything.
• Amylase


  Enzyme within saliva that breaks down carbohydrates
• Organs that make up the digestive system

  • Large Intestine
  • Liver
  • Mouth
  • Pancreas
  • Oesophagus (Gullet)
  • Small intestine
  • Stomach
  • Anus
• Structure of the digestive system

  Mouth → Oesophagus (Gullet) → Stomach → Small intestine → Large intestine → Rectum + Anus
• Categories of enzymes


  • Amylase - Breaks down starches. Found in salivary glands and pancreas.
  • Lipase - Breaks down lipids (fats) into fatty acid and glycerol. Found in pancreas, mouth, stomach.
  • Protease - Pepsin, breaks down proteins. Found in stomach, pancreas and Small Intestine.
• Food Groups


  • Vitamins - A, D, C
  • Carbs - Bread
  • Water - water
  • Minerals (Iron, Calcium) - (milk, yoghourt)
  • Lipids (Fats) - Avocado, Olive oil
  • Protein - Meat
  • Fibre - Beans, broccoli
• The largest organ in the body is the liver
• Small intestines have villi - hair-like projections that increase the surface area
• The large intestine has faeces (always wider)
• Lipids and enzymes are found in the pancreas
• Proteins are found in the stomach, pancreas
• Iodine solution tests for starches
• Benedict's solution tests for sugar
• Vitamin A is important for healthy eyes and skin
• Vitamin B is important for healthy nerves, respiration, and making blood cells
• Vitamin C is important for healthy joints and blood vessels, and makes connective tissue
• Vitamin C deficiency causes scurvy, with symptoms of feeling tired, red/blue spots on skin, and bruising easily
• Vitamin D helps us absorb calcium and keeps our bones and teeth strong. Sunlight causes fat under the skin to change into Vitamin D
• Vitamin D deficiency causes rickets, where the bones in the legs are too tired so they bend
• Aerobic respiration


  Respiration with oxygen
• Anaerobic respiration


  Respiration without oxygen
• Aerobic respiration


  Glucose + Oxygen -> Carbon dioxide + water + ENERGY
• Energy is released in the aerobic respiration reaction, and the mitochondria in the cell cytoplasm are where most of it happens (producing ATP energy)
• Anaerobic respiration


  Glucose -> Lactic acid (Energy - 1 to 2 mins)
• Anaerobic respiration occurs during strenuous exercise, when oxygen is being used up faster than it is being replaced
• Anaerobic respiration occurs in the cytoplasm of muscle cells
• Lactic acid is produced in anaerobic respiration, causing fatigue and muscle soreness (cramp)
• Oxygen debt occurs when the body runs out of oxygen during exercise
• To repay the oxygen debt, you need to stop exercise, your heart rate remains high, your breathing will be rapid, and you need to regain oxygen for energy
• Plants respire anaerobically when they do not have enough oxygen, just like animals
• Plant cells respire anaerobically to produce ethanol and carbon dioxide, as well as energy
• Yeast is an important microorganism in food production, used to make bread, beer and wine through fermentation
• Fermentation


  Glucose -> Ethanol + Carbon dioxide + Energy
• Yeast produces ethanol and carbon dioxide, while muscles produce lactic acid, but both release small amounts of energy
• Bacteria respire anaerobically
• Biogas is a mixture of gases (mainly methane) produced when bacteria break down plant material or human waste
• Methane from biogas can be burnt as a fuel or used to generate electricity
• Biogas generators are used in areas without electricity, using up plant and animal wastes and the leftover material can be used as fertiliser, making them renewable
• Gasohol is a fuel containing a mixture of gasoline and alcohol, mixing alcohol with a fossil fuel makes the non-renewable fossil fuel last longer