b4 - bioenergetics

• photosynthesis

  an endothermic reaction where energy is transferred from the environment to the chloroplast by light
• photosynthesis equation


  carbon dioxide + water ---> glucose + oxygen

  6CO2+6H2O ---> C6H12O6 + 6O2
• 4 factors which can limit the rate of photosynthesis


  1. chlorophyll
  2. light intensity
  3. CO2 concentration
  4. temperature
• limiting the RoP: chlorophyll


  more chlorophyll means that more light can be absorbed which increases the rate of photosynthesis
• limiting the RoP: light intensity


  as light intensity increases there is more energy for the reaction which means the rate of photosynthesis also increases

  Eventually, the line (on graph) will plateau which means that light intensity is no longer the limiting factor - no effect on RoP. temp or CO2 conc becomes the limiting factor
• limiting the RoP: CO2 concentration


  as CO2 conc increases the RoP increases as CO2 is a reactant for photosynthesis

  eventually, the line (on graph) will plateau which means CO2 will no longer be the limiting factor - no effect on the RoP. temp or light intensity will become the limiting factor
• limiting the RoP: temperature


  as the temperature increases there are more collisions between reactant molecules so the rate of photosynthesis increases

  after the optimum temperature, the RoP will fall to zero as higher temp will cause the enzymes to denature
• equation for rate of photosynthesis

  RoP = volume of gas / time
• uses of glucose from photosynthesis


  1. cellular respiration
  2. converted into insoluble starch for storage
  3. fats or oil for storage
  4. cellulose to strengthen cell walls
  5. amino acids for protein synthesis (nitrate ions)
• inverse square law

  light intensity is inversely proportional to the square of the distance between the plant and the light source

  light intensity = 1/distance^2
• cellular respiration

  exothermic reaction which is continuously occurring in the mitochondria of living cells
• organisms uses for energy


  1. chemical reactions build larger molecules
  2. movement
  3. keeping warm
• equation for aerobic respiration

  glucose + oxygen -----> carbon dioxide + water

  C6H12O6 + 6O2 -------> 6CO2 + 6H2O
• equation for anaerobic respiration in muscles


  glucose ---> lactic acid
• anaerobic respiration in plant and yeast cells (fermentation)


  glucose ---> ethanol + carbon dioxide
• aerobic respiration 


  need for oxygen: yes

  products: carbon dioxide and water

  energy transferred: a lot
• anaerobic in animals and bacteria


  need for oxygen: not required

  products: lactic acid

  energy transferred: a little
• anaerobic in plants and yeast (fermentation)


  need for oxygen: not required

  products: ethanol and carbon dioxide

  energy transferred: a little
• metabolism

  sum of all the chemical reactions in the a cell or the body

  energy transferred by respiration in cells is used by the organism for the continual enzyme controlled process of metabolism