Topic 2 - Organisation

• Cell --> Tissue --> Organ --> Organ System
• Teeth break down food mechanically and saliva contains amylase
• The stomach contains hydrochloric acid and enzymes that chemically breakdown food
• The liver produces bile, which is stored in the gallbladder before going to the small intestine. Bile emulsifiers lipids to form droplets, increasing their surface area
• The pancreas secretes amylase which breaks down starch into glucose in the small intestine
• Nutrients like glucose are absorbed into the bloodstream by the villi in the small intestine (starch is too large)
• Water is absorbed into the bloodstream in the large intestine
• Enzymes are proteins that act as biological catalysts
• Enzymes are specific and only break down the substate that fits their active site
• Enzyme activity increases when temperature increases until the temperature is too high and they denature
• Denaturing is when the active site changes shape
• Enzyme Practical:

  1. Add iodine to the spotting tile
  2. Mix amylase with starch, measure temperature and start timer
  3. Add a few drops of the solution into the spotting tile every 30 seconds
  4. Record the time taken for no starch to be present
  5. Record at different temperatures/pH
  6. Optimum pH/temperature is the lowest times
• Carbohydrases break down carbohydrates into simple sugars - e.g amylase breaks down starch into glucose
• Proteases break down proteins into amino acids
• Lipases break down lipids into glycerol and fatty acids
• Starch:

  Iodine from orange to black
• Sugar:

  Benedicts solution from blue to orange/red
• Protein:

  Biuret reagent solution from blue to purple
• Lipids:

  Turns cold ethanol cloudy
• Benedict's solution is the food test you have to heat up before mixing
• Trachea --> Bronchi --> Bronchioles --> Alveoli
• Alveoli (air sacs) have a large surface area to allow gas exchange/diffusion to occur at a fast rate. They are also covered in capillaries to shorten the journey that gas has to travel from the lungs to the bloodstream
• Oxygen diffuses into the bloodstream and binds to the haemoglobin in the red blood cells to be transported around the body
• Carbone and water diffuses out of the bloodtream
• Vena Cava (from body) --> Right atrium --> Right ventricle --> Pulmonary artery (to lungs) --> Pulmonary vein (from lungs) --> Left atrium --> Left ventricle --> Aorta (to body)
• The left side of the heart has thicker walls due to the higher pressure needed to pump blood to the body
• Vavle: prevents backflow
• Double circulatory system: blood enters the heart twice every time it is pumped around the body
• A group of cells near the right atrium create an electrical pulse that causes the heart to contract
• A pacemaker is used when a heart can't pump naturally by itself
• Artery:

  • Carries blood away from heart
  • Thick walls and thin lumen to withstand high pressure
• Vein:

  • Carries blood back to the heart
  • Thin walls and thick lumen to prevent backflow
  • Can be replaced with artificial ones if faulty
• Capillary:

  • One cell thick walls to allow fast diffusion between blood and cell
• CVD (Cardio-vascular disease) - Fat can build up in the arteries, restricting blood flow
• CHD (Coronary heart disease) - when the artery suppling blood to the heart becomes blocked
• Solutions to CHD:

  • Stent - a mesh-like metal pipe that opens up the vessel by expanding
  • Statins - drugs that reduce fatty deposits
• Blood carries red blood cells, white blood cells and platelets (for clotting). Everything except oxygen is dissolved in the plasma
• Plant organs:

  • Leaf - photosynthesis,gas exchange and water evaporates out
  • Flower - reproductive organ
  • Meristem - stem cell production
  • Roots - water enters through osmosis, mineral ions by active transport
• Xylem:

  • Plant organ
  • Continuous tubes that carry water and dissolved mineral ions upwards
  • Transpiration (unidirectional) rate increase with increase air movement or temperature and decrease humidity
• Phloem:

  • Tubes of cells that carry sugars and other nutrients to where needed
  • Translocation - bidirectional