bits of biology

• • Artery walls have thick layers of muscle. This makes them strong and able to cope with the high pressure at which blood is pumped out by the heart.
• • The walls of a vein are thinner than those found in the arteries as the blood is at a lower pressure.
• • Veins have valves to prevent the backflow of blood.
• • In capillaries, waste products, such as carbon dioxide, move out of the cells and into the blood.
• capillaries branch out from arteries and have thin walls
• In capillaries, food and oxygen move out of the blood and into the cells.
• Arteries branch into much smaller vessels, called capillaries. Capillaries have thinwalls and pass very close to the body cells.
• antibodies Lock onto pathogens, effectively ‘tagging’ them.
• an antigen is a foreign substance that is recognized by the immune system as a foreign invader
• A vaccination injects a dead or inactive form of a pathogen into the blood.
• process of vaccine :

  1. A vaccination injects a dead or inactive form of a pathogen into the blood.
  2. White blood cells recognise that the antigens are foreign and produce antibodies against them
  3. some of these white blood cells remain in the blood as memory cells.
  4. If the same pathogen invades the body again, the memory cells are able to produce antibodies fasterand produce more antibodies
  5. Next time the same pathogen infects the vaccinated person, it will be destroyedby the immune system before it can cause illness.
• respiration is the process of transferring energy from glucose which goes into the cells
• example of how organisms use the energy from respiration

  • to build up larger molecules from smaller ones
  • to allow muscles to contract
  • used to keep body temperature steady in colder a surroundings (in mammals and birds)
• metabolism is all the chemical reaction is an organism
• lots of small glucose molecules are joined together to from starch , glycogen and cellulose
• lipid molecules are each made from one molecule of glycerol and fatty acids
• what is the equation for aerobic respiration ?


  glucose + oxygen --> carbon dioxide + water
• most of the reactions in aerobic reparation take place in the mitochondria
• anaerobic respiration is used if there isn't enough oxygen
• in anaerobic respiration lactic acid builds up which causes muscle pain
• when you do vigorous exercise and your body can't supply oxygen to your muscles they start doing anaerobic respiration
• anaerobic respiration is the incomplete breakdown of glucose , making lactic acid
• anaerobic respiration equation :

  glucose --> lactic acid
• anaerobic respiration doesn't transfer nearly as much energy than aerobic respiration
• plants and yeast cells can respire without oxygen but they produce ethanol and carbon dioxide instead of lactic acid
• what is the equation for anaerobic respiration in plants and yeast cells ?

  glucose ---> ethanol + carbon dioxide
• anaerobic respiration in yeast cells is called fermentation
• when you exercise you respire more because

  • when you exercise your muscles contract more frequently so you need more energy
  • the increase in respiration in your cells means you need to get more oxygen into them
• after resorting to anaerobic respiration , when you stop exercising you'll have oxygen debt
• an oxygen debt is is the amount of extra oxygen your body needs to react with with the build up of lactic acid and remove it from the cells
• microscopy practical

  1. place tissue sample on microscope slide
  2. add few drops of stain (iodine )
  3. place a coverslip on tissue
  4. draw any type of cells that can be seen
• osmosis practical

  1. cut up potatoes into equal cylinders and get some beakers with different sugar solutions in them
  2. measure the mass of the cylinders
  3. leave one cylinder in each beaker and.leave for 24 hours
  4. measure the masses again
  5. (if cylinders have down in water mass will have increased, if water has been drawn out mass will have decreased )
• osmosis practicle

  INDEPENDENT VARIABLE = concentration of sugar solutions

  DEPENDANT VARIABLE= chip mass

  CONTROL VARIABLE = volume of solution
• effect of pH on amylase

  1. add one drop of iodine into well of spotting tile
  2. get three test tubes
  3. fill one with starch solution another with amylase solution and the last one with ph 5 buffer solution
  4. place test tubes in water bath for 5 minutes
  5. combine the 3 solutions and stir
  6. put back in water bath and start stopwatch
  7. after 30 seconds transfer one drop of solution from test tube into a well of the spotting tile
  8. iodine should go blue/black
  9. every 30 seconds do this with other wells until iodine remains orange which means starch has been digested
• photosynthesis practicle

  1. place boiling tube 10 cm away from LED light
  2. fill boiling tube with solution
  3. put piece pondweed into boiling tube (with cut end at top)
  4. leave for 5 minutes then bubbles of gas will be produced
  5. start stopwatch and count how many bubbles produced in one minute
  6. repeat experiment but place boiling tube 20 cm away then 30 cm away
• phloem have very FEW SUBCELLULAR STRUCTURES to help substances flow through easily
• • xylem are HOLLOW for easy flow.
  • xylem are made up of dead cells strengthened with LIGNIN.
• therapeutic cloning is the process of creating an embryo that has the same genetic material as the patient
• advantages of therapeutic cloning

  • no risk of rejection
  • cells of any type can be produced
• disadvantages of therapeutic cloning

  • potential life is destroyed
  • may transfer infection
  • poor success rate