Organisation

• Cells


  Fundamental units (building blocks) of all living organisms
• Tissues


  Groups of similar cells that act together to perform a similar function
• Organ


  A group of distinct tissues that work together to perform a specific function
• Organ systems


  Groups of organs that work together to perform a particular role
• Organs in the digestive system

  • Glands
  • Stomach
  • Liver
  • Small intestine
  • Large intestine
• What do the glands do?

  • Produce digestive juices
• What does the Liver produce?

  • Produces bile
• Function of the Small intestine

  • Digests food and absorbs soluble (can be dissolved) food molecules
• Function of the Large intestine

  • Absorbs water molecules from the remaining undigested food, allowing it to produce faeces
• Enzymes

  Enzymes increase the speed of reactions, often called biological catalysts
• Active site of an enzyme

  • To catalyse (speed up) a reaction, the reacting chemical (substrate) must bind to the enzyme's active site
  • The active site will only fit specific substrates
• Lock and key

  The active site is like a lock and the substrate is like a key
• Factors Affecting the Rate of Enzyme Action

  • Temperature
  • pH (measure of acidity)
• Effect of temperature on enzyme action

  1. Increasing temperature initially increases reacting activity

  2. Enzymes have an optimum temperature

  3. Past a certain temperature, the active site changes shape and the enzyme is denatured (loses its catalytic activity)
• Optimum pH

  The pH at which an enzyme functions best
• If the pH changes away from the optimum pH the enzyme activity decreases
• If the pH is too low or too high, the enzyme is denatured and will not function
• Digestive enzymes

  Enzymes made by specialised cells in the glands and the lining of the gut, then secreted out of the body cells and into the cavity of the digestive system
• Digestive enzymes

  1. Breakdown of large food molecules

  2. Catalyse (speed up) the breakdown of large, insoluble food molecules into smaller, soluble (can be dissolved) molecules

  3. Digested molecules can be used to construct new carbohydrates, proteins and lipids in the body

  4. Some glucose produced by digestion is used for respiration
• Main digestive enzymes

  • Amylase
  • Protease
  • Lipase
• Name the tubes that split off the trachea

  Bronchi
• Testing for carbohydrates, lipids and proteins

  1. Grind up the food and add distilled water to dissolve some of the food

  2. Test for the food substances
• Starch test

  Add iodine solution, it will turn blue-black if starch is present
• Sugar test

  Add Benedict's reagent and heat, it will turn any of green, yellow or red if sugar is present (colour depends on concentration)
• Protein test

  Add Biuret solution, it will turn mauve or purple if proteins are present
• Lipid test

  Add Sudan III, if lipids are present a red-stained oil layer will float on the water surface
• Proteases

  A type of digestive enzyme that breaks down proteins into amino acids
• Lipase

  A type of digestive enzyme that breaks down lipids into glycerol and fatty acids
• Amylase

  A type of carbohydrase that breaks down starch into its constituent simple sugars (predominantly maltose)
• Production of amylase

  Small intestine, Salivary glands, Pancreas
• Production of lipase

  Small intestine, pancreas
• Production of proteases

  Small intestine, pancreas, stomach
• Bile

  An alkaline substance that is stored in the gall bladder after having been produced in the liver
• Optimal enzyme conditions

  Enzymes in the small intestine operate best in alkaline conditions
• Bile neutralises acid from the stomach to stop enzymes becoming denatured (lose their activity)
• What happens during ‘Emulsification‘

  Bile breaks up fats into tiny droplets
• What are the 3 main blood vessels blood moves around the body in?

  Arteries, veins, capillaries
• The heart recieves deoxygenated blood from the body through a vein called the vena cava
• The heart receives oxygenated blood from the lungs through the pulmonary vein
• The heart pumps out oxygenated blood to the body though the aorta