Bioenergetics

• Photosynthesis 


  The process by which plants use light energy to create their own food
• Equation for photosynthesis 


  COW >(light) GO

  6CO2 + 6H2O >(light) C6H12O6 + 6O2
• Plants have chloroplasts which contain chlorophyll (green pigment) which absorbs light energy for photosynthesis
• Photosynthesis is an endothermic reaction - energy beig taken in from the surroundings
• Use of glucose in photosynthesis

  • to produce energy in respiration
  • forms cellulose to strengthen cell walls
  • stored in starch in the leaves, stems, roots of a plant
  • can also be stored in the fats and oils of the seed
• Limiting factors of photosynthesis

  • light intensity
  • temperature
  • carbon dioxide
• Ideal environment of plants

  • glass structure traps heat from the sun to keep plants warm
  • glass panes allow lots of light
  • artificial lights at night to keep plants photosynthesising
  • paraffin heaters used to increase the amount of CO2
• Respiration 


  The process by which all living cells continuously release energy from glucose
• Aerobic respiration

  • the respiration using oxygen
  • the most efficient way to transfer energy from glucose
  • happens all the time in plants and animals
  • takes place in the mitochondria
• Aerobic respiration equation

  Glucose + oxygen > carbon dioxide + water (+energy)

  C6H12O6 + 6O2 > 6CO2 + 6H2O
• Anaerobic respiration

  • used if there’s not enough oxygen
  • glucose isn’t fully oxidised, so it’s much less efficient than aerobic respiration
  • only useful in emergencies e.g. doing exercise
• Anaerobic respiration in muscles equation 


  Glucose > lactic acid
• Anaerobic respiration in plants and yeast cells equation

  Glucose > ethanol + carbon dioxide
• Anaerobic respiration in plants and Yeast

  • anaerobic respiration in yeast cells is called fermentation
  • fermentation is important as it’s used to make bread, beer, and wine
• Metabolism 


  All the chemical reactions that happen within a cell or organism
• Plant metabolism

  • plants carry out respiration and create their own glucose using photosynthesis
  • glucose can be stored as lipids or starch, and converted back when required
  • glucose used to make cellulose (provides strength to cell walls)
• Animal metabolism

  • animals intake large molecules in food and get digested by enzymes
  • glucose used for respiration or stired as glycogen in liver and muscles until needed
  • amino acids used to build new proteins. excess converted into urea
  • fatty acids and glycerol converted back to lipids to build new cell membranes
• • If animals don’t have sufficient glucose in bloodstream for respiration, body will break down its stores of glycogen
  • if body runs out if glycogen, it will break down fat stores (proteins) as a last resort