Bioenergetics

• Limiting factors


  Important in the economics of enhancing the conditions in greenhouses to gain the maximum rate of photosynthesis while still maintaining profit
• Products of photosynthesis


  • Used for respiration
  • Converted into insoluble starch for storage
  • Used to produce fat or oil for storage
  • Used to produce cellulose, which strengthens the cell wall
  • Used to produce amino acids for protein synthesis
• To produce proteins, plants also use nitrate ions that are absorbed from the soil
• Organisms need energy for


  • Chemical reactions to build larger molecules
  • Movement
  • Keeping warm
• Aerobic respiration


  glucose + oxygen -> carbon dioxide + water
• Anaerobic respiration in muscles

  glucose -> lactic acid
• As the oxidation of glucose is incomplete in anaerobic respiration much less energy is transferred than in aerobic respiration
• Anaerobic respiration in plant and yeast cells

  glucose -> ethanol + carbon dioxide
• Anaerobic respiration in yeast cells


  Fermentation and has economic importance in the manufacture of bread and alcoholic drinks
• Human body's reaction to increased demand for energy during exercise


  1. Heart rate increases

  2. Breathing rate increases

  3. Breath volume increases

  4. To supply muscles with more oxygenated blood
• If insufficient oxygen is supplied, anaerobic respiration takes place in muscles
• Incomplete oxidation of glucose causes a build up of lactic acid and creates an oxygen debt
• During long periods of vigorous activity, muscles become fatigued and stop contracting efficiently
• Removal of lactic acid from muscles


  1. Blood transports lactic acid to the liver

  2. Liver converts lactic acid back into glucose
• Oxygen debt

  The amount of extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells
• Metabolism


  The sum of all the reactions in a cell or the body
• The energy transferred by respiration in cells is used by the organism for the continual enzyme controlled processes of metabolism that synthesise new molecules
• Processes included in metabolism


  • Conversion of glucose to starch, glycogen and cellulose
  • Formation of lipid molecules from a molecule of glycerol and three molecules of fatty acids
  • Use of glucose and nitrate ions to form amino acids which in turn are used to synthesise proteins
  • Respiration
  • Breakdown of excess proteins to form urea for excretion