B2 - organisation

• where can human specialised cells be found

  • sperm
  • nerve
• where can plant specialised cells be found

  • root hair
  • xylem
  • phloem
• what are enzymes

  • biological catalysts - they speed up chemical reactions
  • large protiens
  • work best at 37 degrees and certain pH
• enzymes in the digestive system

  • pass out of the cells into the degestive system
  • come into contact with food molecules
  • they speed up the breakdown of large insoluble food molecules into smaller ones
• food tests - required practical

  • to test for sugars - add benedicts solution and heat in a water bath for 2 mins, if it turns red, sugar is present
  • to test for starch - add iodine solution, if starch is present, it will turn blue / black
  • to test for protien - add biuret reagent, if portien is present, it will turn purple
• amylase

  • produced in salivary glands and the pancreas
  • carbohydrase that breaks starch down into sugars
  • is later broken into glucose
• protease

  • produced in the stomach
  • breaks protiens down into amino acids
• lipase

  • produced in the pancreas and small intestine
  • nreaks down lipids into fatty acids and glycerol
• what is bile

  • liquid made in the liver and stored in the gallbladder
  • emulsifies fat to form small droplets, increasing the surface area for enzymes to act on
  • alkaline to neutralise the hydrochloric acid in the stomach
• pH on amylase - required practical

  • place a test tube of starch solution + a test tube of amylase in a waterbath of 37 degrees
  • after 5 mins add the amylase to the starch
  • every 30 seconds tak a drop from the mixture and test it for starch
  • record how long it takes for the starch to be digested
  • repeat the experiment using different pH values
• what is blood

  a tissue made from a liquid called plasma consisting of 3 different components. red / white blood cells and platelets.
• red blood cells

  • contains haemoglobin (binds to oxygen to transport it to where it is needed for respiration)
  • doesnt contain a nucleus
  • very small
• white blood cells

  • protects the body against infection
  • can change shape for movement
• platelets

  fragments of dead cells, trigger blood clotting.
• blood vessels

  • arteries - transport blood from the heart to organs, thick walls made from muscle
  • veins - transport blood from organs to the heart, thinner walls with valves
  • capillaries - allow substances needed by the cells to pass out of the blood / into the blood, narrow and thin
• double circulatory system

  • blood enters heart through the atria
  • atria contact and force blood into ventricles
  • ventricles contact and force blood out of the heart
  • valves make sure the blood flows in the right direction
  • resting heart rate is controlled by a pacemaker (a group of cells in right atrium)
• risk factors

  • cardiovascular disease - lack of exercise, smoking
  • type 2 diabetes - obesity
  • low birth weight - smoking during pregnancy
• coronary heart disease

  layers of fatty meterial build up inside the corornary arteries and narrow them. treatments include stent (keep arteries open), statin (prescribed to lower blood cholesterol levels)
• water transport in plants

  • water enerts the plant through root hair cells. the water contains dissolved minerals
  • then transported through the xylem
  • at the leaves, water will evaporate through the stomata. the loss of water through leaves is transpiration
• factors affecting the rate of transpiration (water)

  • increase in temperature increases the rate
  • increased light will increase the rate as it will cause the stomata to open