b4

• limiting factor - reduces the rate of reaction
• rpa

  1. set up test tube rack 10cm away from light source
  2. fill boiling tube with sodium hydrogen carbonate (increases conc of co2 to stop it being a limiting factor)
  3. add piece of pondweed to boiling tube
  4. leave for 3 minutes to allow pondweed to adjust to new light intensity
  5. start stop watch and count number of bubbles produced in 1 minute
  6. write down results and repeat to calculate mean and cancel anomalies
  7. repeat at distances of 20cm and 30cm from light source
• aerobic

  • uses oxygen
  • yields the most energy
  • most of it occurs in the mitochondria
  • products: water and co2

  anaerobic

  • occurs when theres not enough oxygen
  • doesnt yield as much energy
  • used if oxidation of glucose is incomplete
• anaerobic

  c6h6o6 + oxygen = lactic acid (in animals)

  c6h12o6 + oxygen = ethanol + co2 (in plant and yeast cells - fermentation, used to make bread and alcohol)
• glucose is stored as starch because it is insoluble meaning it wouldn't swell cells. glucose is soluble so water can enter through osmosis and swell up.

  starch is stored in the roots, stem and leaves of the plant.
• nitrates are needed to make proteins, increases the rate of protein synthesis, grows quicker and larger
• glucose is used for

  • respiration
  • making cellulose - strong plant cell walls
  • making amino acids - combined with nitrate ions to make amino acids which are then made into proteins
  • stored as fats or oils (stored in seeds)
  • stored as starch
• greenhouse = increases temperature to make sure it doesnt become limiting factor, keeps plant enclosed and away from pests and disease

  shades and ventilation - cools things down if its too hot

  commercial farms use artificial light after the sun goes down

  paraffin heater = increases co2
• respiration is exothermic, transfers energy from glucose into every cell
• use of energy transferred by respiration

  • to build up larger molecules from smaller ones
  • all the muscles to contract
  • keep body temperature steady
• exercise = muscles contract more frequently, more energy required = more respiration

  for more respiration = more oxygen needed

  = breath volume and breathing rate increase for more oxygen in the blood

  haemoglobin takes oxygen from lungs around the body

  at the same time co2 is removed more quickly
• vigorous exercise = body cant supply enough oxygen so you start respiring anaerobically

  lactic acid builds up in muscles causing muscle fatigue = muscles stop contracting efficiently
• after vigorous exercise and respiring anaerobically, body enters oxygen debt

  this means more oxygen is needed to react with the lactic acid to remove it (it forms harmless co2 and water)

  this means you have to breath hard for more oxygen into your blood which is transported to muscle cells

  pulse and breathing rate stay high when there is high levels of lactic acid and co2

  another way is the blood that enters the muscle transfers the lactic acid to the liver where it converted back to glucose
• examples of metabolic reactions

  • respiration
  • glucose and nitrate irons forming amino acids
  • urea forming the break down of proteins for excretion
  • glucose molecules converted into starch, glycogen and cellulose