Bioenergetics

• Photosynthetic reaction

  Carbon dioxide + water → glucose + oxygen
• CO2


  Carbon dioxide
• Rate of photosynthesis


  • Determined by temperature, light intensity, carbon dioxide concentration and the amount of chlorophyll present
• Factors can interact


  A higher light intensity can lead to a higher temperature
• Knowledge of these factors can help improve crop yield and make farming more efficient
• Uses of glucose


  • Used in respiration
  • Used to produce amino acids which are combined with nitrates (from soil) to produce proteins
  • Used to produce cellulose for cell walls
  • Stored as starch (insoluble)
  • Used to produce fats/oils for storage
• Light intensity


  Obeys the inverse square law
• Higher light intensity


  More energy for photosynthesis
• Photosynthesis is an endothermic process
• Increasing the supply of a limiting factor increases the rate of photosynthesis
• Photosynthesis can be controlled using a greenhouse
• Metabolism


  The sum of all metabolic reactions in a cell or an organism
• Functions of respiration

  • Exercise
  • Metabolism
  • Synthesis using glucose
• Types of respiration

  • Aerobic
  • Anaerobic
• Aerobic respiration


  • Glucose + oxygen → carbon dioxide + water
  • Produces more energy
• Anaerobic respiration


  • Glucose → ethanol + carbon dioxide
  • Glucose → Lactic acid
  • Produces less energy
• Anaerobic respiration in yeast and plants


  • Produces ethanol
  • Used in making bread and alcoholic drinks
• Anaerobic respiration in muscles

  • Produces lactic acid
  • Leads to oxygen debt
  • Causes muscle fatigue
• Higher demand for energy

  • Higher heart rate
  • Higher breathing rate
  • Higher breath volume
  • Supply oxygenated blood at a higher rate to muscles
• Insufficient oxygen


  Build up of lactic acid
• Removal of lactic acid

  1. Lactic acid is converted to glucose in the liver

  2. Additional volume of oxygen needed to react with lactic acid to remove it from the cells
• Anabolic reactions

  • Synthesis of lipids (glycerol + 3 fatty acids)
  • Synthesis of amino acids (requires glucose and nitrates)
  • Making proteins
  • Excess proteins are broken down to urea
• Catabolic reactions

  • Breakdown of glycogen
  • Breakdown of starch
  • Breakdown of cellulose
• Respiration is exothermic and releases energy