Biology topic 4

• photosynthesis taken place in the chloroplast which contains pigments like chlorophyll which absorb light
• photosynthesis is an endothermic reaaction, meaning it takes in energy from the surroundings
• carbon dioxide + water -> glucose + oxygen
• 6CO2 + 6H2O -> C6H12O6 + 6O2
• uses of glucose

  1. respiration - transfers energy from glucose enabling plant to convert the rest of the glucose into useful substances
  2. making cellulose - glucose converts into cellulose providing a strong cell wall
  3. oil / fats - glucose turned into lipids for storing seeds
  4. amino acids - glucose combined with nitrate ions to produce amino acids which turn into proteins
  5. starch - glucose turned to starch (insoluble) and stored in roots, stems, leaves ready for photosynthesis
• affect of light on photosynthesis

  1. provides energy for photosynthesis
  2. brighter means increased photosynthesis - until certain point where co2 and temp are limiting factors
• affect of co2 on photosynthesis

  1. increases rate of photosynthesis to certain point
• affect of temperature on photosynthesis

  1. slow at low temperatures
  2. too hot and the enzymes become denatured
• measuring rate of photosynthesis

  1. place pondweed set distance away from light
  2. leave to photosynthesise for certain time - oxygen released will be collected into a capillary tube
  3. at end syringe used to draw out gas bubbles in the tube alongside a ruler and the length of the gas bubble is measured - proportional to oxygen produced
  4. repeat with light at different distances
• measuring how temp affect photosynthesis

  place test tube of the pondweed in water bath
• measuring how co2 affect rate of photosynthesis

  measure amount of sodium hydrogen carbonate dissolved in water
• light intensity ∝ 1 / distance ^2
• artificially farming conditions

  1. greenhouses - trap suns heat
  2. increase levels of co2 using a paraffin heater as it burns it releases co2
  3. plants enclosed so free from pests and diseases
  4. add fertilisers and provide minerals
  5. successful
• respiration is the process of transferring energy from the break down of glucose
• respiration

  1. takes place in every cell
  2. exothermic reaction
• use of respiration

  1. builds up larger molecules from smaller ones ~
  2. animals - allows the muscles to contract
  3. mammals and birds - energy used to keep body temperature steady in colder surroundings
• aerobic respiration

  1. uses oxygen - most efficient way to transfer energy from glucose
  2. happens all the time in mitochondria
• aerobic respiration


  glucose + oxygen -> carbon dioxide + water
• aerobic respiration 


  C6H12o6 + 602 -> 6CO2 + 6H2o
• Anaerobic respiration

  1. happens during exercise when the body cant supply enough oxygen to muscles
  2. without oxygen
  3. doesnt transfer a lot of energy as its not fully oxidised
• anaerobic respiration in muscle cells

  glucose -> lactic acids
• anaerobic respiration in plants and yeast

  glucose -> ethanol + carbon dioxide
• in cells lots of chemical reactions happen all the time that are controlled by enzymes, many reactions link to form bigger ones
• in some reactions larger molecules are made from small molecules
• in some reactions large molecules are broken down into smaller ones
• metabolism is the sum of all reactions that happen in a cell or the body
• 1. muscles need energy from respiration to contract when exercising more often
  2. so need more energy
  3. so more respiration is needed
  4. so more oxygen is needed in cells
  5. so breathing rate and volume increases and heartrate increases so oxygenated blood is pumped faster
• vigorous exercise means body cant supply enough oxygen to cells so body starts anaerobically respiring - this is not the best way to transfer energy as lactic acid builds up which is painful
• oxygen debt

  1. after resorting to anaerobic respiration when you stop exercising you will be in oxygen debt
  2. its the amount of extra oxygen your body needs to react with the build up of lactic acid and remove it - when they react it forms co2 and h2o
• the body also copes with high levels of lactic acid by the blood that enters he muscles transports the lactic acid to the liver where it is converted back to glucose
• 2 uses of energy released in respiration

  1. active transport
  2. help muscles contract
• explain why the death of a pond snail caused the concentration of co2 to increase

  snail was been broken down by the decomposers bacteria so they respire which releases co2
• what is water is taken in by the roots of a plant and lost from the leaves called

  transpiration stream
• a larger surface area to volume ratio means that heat is lost quicker so it requires a greater amount of respiration which means a large metabolism rate to generate heat
• explain the overall change of co2 and o2 at different light intensities

  1. dim light - no overall exchange of c02 and o2 as the rate of respiration = rate of photosynthesis meaning the co2 released in respiration must be used in photosynthesis and o2 used in respiration is released from photosynthesis
  2. no light - no photosynthesis so no co2 released and no o2 needed - but respiration happens all the time so co2 constantly created
  3. bright light - higher rate of photosynthesis then respiration
• TMV can cause plants to produce less chlorophyll why might this mean stunted growth 


  there will be less photosynthesis because of the lack of chlorophyll therefore less glucose is made so less energy is released for growth because energy is needed for respiration and therefore less proteins for growth because glucose is needed to make protein
• aerobic respiration produces water where as anaerobic respiration produces lactic acid
• aerobic respiration releases more energy
• aspirin originated form willow
• digitalis originated from foxgloves