Bioenergetics

• Photosynthesis

  The reaction that plants use to trap light energy
• Plants use light for their source of energy
• Photosynthesis

  • It is an endothermic reaction
  • It takes place in the leaves of a plant
  • Leaves contain the green chemical chlorophyll
• Photosynthesis

  1. Plant takes in carbon dioxide and water

  2. Light energy is absorbed by chlorophyll

  3. Light energy is used to convert carbon dioxide and water into glucose

  4. Oxygen is also produced
• Chemical formulas

  • Carbon dioxide (CO2)
  • Water (H2O)
  • Glucose (C6H12O6)
  • Oxygen (O2)
• Light intensity increases

  Rate of photosynthesis increases
• Light intensity is a limiting factor

  Photosynthesis is not as fast as it could be because there isn't enough light
• Carbon dioxide level increases

  Rate of photosynthesis increases
• Carbon dioxide is a limiting factor

  Photosynthesis is not as fast as it could be because there isn't enough carbon dioxide
• Factors affecting rate of photosynthesis

  • Amount of chlorophyll in the leaf
  • Temperature
• Temperature increases

  Enzymes involved in photosynthesis work faster, increasing the rate
• Temperature keeps increasing

  Enzymes denature, decreasing the rate of photosynthesis
• Photosynthesis

  Carbon dioxide + water + light energy → Glucose + Oxygen
• Respiration

  Process that releases energy from glucose in the mitochondria
• Photosynthesis only produces glucose during the day

  Plant cells respire all the time, including at night
• Starch

  Insoluble storage molecule made from glucose, which can be converted back to glucose when needed
• Fats and oils

  Storage form of energy made from glucose in many plants
• Cellulose

  Molecule in the plant cell wall that gives it strength, made from glucose
• Amino acids

  Made from glucose, used by plants to synthesize proteins
• Peas are a good protein source
• Plants need to absorb nitrate ions from the soil to make amino acids from glucose
• Photosynthesis

  Process where light energy is absorbed by chlorophyll and used to react carbon dioxide with water to make the sugar glucose, with oxygen as a product
• Interpreting graphs to determine limiting factor in photosynthesis

  1. Increase light intensity

  2. Observe rate of photosynthesis

  3. Light intensity is limiting factor

  4. Increase carbon dioxide concentration

  5. Observe rate of photosynthesis

  6. Carbon dioxide concentration is limiting factor

  7. Increase temperature

  8. Observe rate of photosynthesis

  9. Temperature is limiting factor
• Limiting factors in photosynthesis

  • Light intensity
  • Carbon dioxide concentration
  • Temperature
  • Amount of chlorophyll
• Increasing light intensity

  Rate of photosynthesis increases
• Increasing carbon dioxide concentration

  Rate of photosynthesis increases
• Increasing temperature

  Rate of photosynthesis increases, but too high temperature causes enzymes to denature and rate to fall
• Greenhouse

  Used by farmers to increase rate of photosynthesis and crop yield, by providing extra light, heat, and carbon dioxide
• Increasing rate of photosynthesis in greenhouses has to be justified by the increase in crop yield, as it is expensive to provide extra light, heat and carbon dioxide
• Respiration

  A process that supplies the energy needed for biological processes
• Respiration is an exothermic reaction because it releases energy and it takes place continually in all living cells
• Types of respiration

  • Aerobic respiration
  • Anaerobic respiration
• Aerobic respiration

  1. Glucose reacted with oxygen gas

  2. Produces carbon dioxide and water

  3. Releases energy
• Aerobic respiration

  Glucose molecule has been fully oxidized
• Glucose

  Oxygen
• Carbon dioxide

  Water
• Anaerobic respiration in muscles

  1. Glucose converted to lactic acid

  2. Does not require oxygen
• Anaerobic respiration

  • Releases much less energy than aerobic respiration
  • Oxidation of glucose is incomplete
• Anaerobic respiration in plants and yeast

  1. Glucose converted to ethanol and carbon dioxide

  2. Does not require oxygen
• Fermentation

  Anaerobic respiration in yeast cells used to make alcoholic drinks and bread