Organisation

• Human digestive system

  • Glands (Salivary + Pancreas) produce digestive juices containing enzymes to break down food (amylase)
  • Stomach produces HCl acid to kill bacteria and provide optimum PH for pepsin (protease) to work
  • Small intestine is where soluble molecules are absorbed into the blood
• Human digestive system

  • Liver produces bile which is stored in the gallbladder, helps digest lipids
  • Large intestine absorbs water from undigested food to produce faeces. Passes through the rectum and anus
• Enzymes?

  Biological catalysts that are proteins
• 5 properties of enzymes

  • All proteins
  • Control one specific reaction
  • Reusable
  • Affected by temperature
  • Affected by PH
• Amylase?

  • Turns carbohydrates to sugars
  • Produced in salivary glands/pancreas/small intestine
• Protease?

  • Turns proteins to amino acids
  • Produced in stomach/pancreas/small intestine
• Lipase?

  • Turns fats to fatty acids + glycerol
  • Produced in pancreas/small intestine
• Food tests

  • Starch - Iodine test (orange) turns blue-black
  • Sugar - Benedict's test (blue) turns brick red
  • Protein - Biuret test (blue) turns purple
  • Lipids - Emulsion test (ethanol + water) forms a cloudy layer
• 4 components of blood?

  • Red blood cells
  • White blood cells
  • Plasma
  • Platelets
• Artery

  • Carries blood away from the heart
  • Small and narrow lumen
  • Thick layers of muscle and elastic tissue
  • Can stretch and spring back
• Vein

  • Carries blood to the heart
  • Wider lumen
  • Thinner layers of muscle and elastic tissue
  • Valves to avoid backflow of blood
• Capillaries

  • Gases diffuse from blood to cells of the body
  • Very small lumen
  • One cell thick
  • Semi permeable walls to allow diffusion of gases and nutrients
• Blood flow

  • Deoxygenated - into the right atrium and the right ventricle which pumps to the lungs for gas exchange
  • Oxygenated - into the left atrium and the left ventricle which pumps blood around the body
• Process of blood in the heart

  1. Blood flows to the right atrium through the vena cava, then the left atrium through the pulmonary vein
  2. Atria contract forcing blood to the ventricles
  3. Ventricles contract pushing the blood into the right ventricle to the pulmonary artery to the lungs. Blood in the left ventricle to the aorta to go around the body
  4. Valves close to prevent backflow
• Alveoli

  • To make gas exchange in the lungs efficiently
  • Moist thin walls
  • Give the lungs a large surface area
  • Have tiny blood vessels called capillaries