Topic 4: 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
• Limiting factor


  The factor that is in short supply and is limiting the rate of photosynthesis
• Carbon dioxide level increases

  Rate of photosynthesis increases
• Factors affecting rate of photosynthesis


  • Light intensity
  • Carbon dioxide level
  • Amount of chlorophyll in leaf
  • Temperature
• As temperature increases, enzymes involved in photosynthesis work faster, but if temperature keeps increasing, enzymes will denature and rate of photosynthesis will fall
• Photosynthesis formula


  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
• Plants need to absorb nitrate ions from the soil to make amino acids from glucose
• 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
• 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
• Respiration


  The process that provides energy for the body
• Types of respiration


  • Aerobic
  • Anaerobic
• When resting


  The body doesn't need a great deal of energy
• During exercise


  The body needs a great deal of energy for muscle contraction
• Aerobic respiration increases during exercise


  1. Breathing rate increases

  2. Breathing volume increases

  3. Heart rate increases

  4. More oxygen supplied to the bloodstream
• During intense exercise


  Anaerobic respiration takes place in the muscles
• Anaerobic respiration


  Oxidation of glucose is incomplete, leading to a buildup of lactic acid
• Lactic acid buildup


  Causes muscle fatigue and inefficient muscle contraction
• Removing lactic acid from muscles


  1. Lactic acid transported to liver

  2. Converted back to glucose

  3. Requires oxygen
• Oxygen debt


  The amount of extra oxygen the body needs after exercise to deal with the accumulated lactic acid
• Metabolism


  The sum of all the chemical reactions in a cell or the body
• Metabolism


  1. Converts glucose into

  2. Cellulose (strengthens plant cell wall)

  3. Starch (storage form of glucose)

  4. Amino acids (used to synthesize proteins)
• Glycogen


  A storage form of glucose in humans and other animals