B4 - Bioenergetics

• Equation for photosynthesis 


  Carbon dioxide + water = glucose + oxygen

  6CO2 + 6H2O = C6H12O6 + 6O2
• Stages of photosynthesis

  1. Uses energy to change co2 and water into glucose and oxygen
  2. Takes place in chloroplasts in green plant cells, they contain chlorophyll that absorb the light
  3. Energy is transferred to the chloroplasts from the environment by light
  4. This reaction is endothermic
• Ways plants use glucose

  1. Respiration
  2. Making cellulose
  3. Amino acids
  4. Stored as oils or fats
  5. Stored as starch
• Limiting factors affecting photosynthesis

  • Light if its dark
  • Temperature e.g. winter
  • co2 if its warm and bright enough
  • the amount of chlorophyll
• Equation for light intensity

  1/distance2
• Respiration


  The transferring energy from the breakdown of glucose which happens in every cell
• Examples of how respiration is used

  1. Build up of larger molecules from smaller ones
  2. In animals, allows muscles to contract
  3. Mammals and birds, energy is used to keep their body temp warm
• Metabolism 


  The chemical reactions in an organism controlled by enzymes
• Aerobic respiration

  • Needs oxygen
  • Most efficient way to transfer energy from glucose
  • Goes on all the time in plants and animals
  • Happens inside mitochondria
• Equation for aerobic respiration

  glucose + oxygen = carbon dioxide + water

  C6H1206 + 6O2 = 6CO2 + 6H2O6
• Anaerobic respiration

  • Occurs when you do excessive exercising and the body cannot supply enough oxygen
  • Incomplete breakdown of glucose
  • Does not transfer enough energy
  • Only useful in emergencies
• Equation for anaerobic respiration

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

  • plants and yeast can respire without oxygen
  • they produce ethanol and CO2 instead of lactic acid
  • anaerobic respiration in yeast cells is called fermentation
  • fermentation by yeast is used to make bread and alcohol like beer or wine
  • CO2 is for bread making
  • fermentation process produces ethanol (alcohol)
• equation for anaerobic respiration in plants and yeast

  glucose -> ethanol + carbon dioxide