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
• Temperature increases

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

  Enzymes denature, causing the rate of photosynthesis to fall
• Other factors that can affect the rate of photosynthesis are the amount of chlorophyll in the leaf
• 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 produced from glucose
• Glucose produced in photosynthesis

  Can be converted back to starch when needed by the plant
• Fats and oils


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

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

  Produced from glucose, used by plants to synthesize proteins
• 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
• Photosynthesis

  1. Light energy absorbed by chlorophyll

  2. React carbon dioxide with water

  3. Make sugar glucose

  4. Oxygen produced
• Limiting factors in photosynthesis

  • Light intensity
  • Carbon dioxide concentration
  • Temperature
  • Amount of chlorophyll in leaves
• Light intensity increases

  Rate of photosynthesis increases
• Light intensity is the limiting factor

  Rate of photosynthesis is limited by light intensity
• Carbon dioxide concentration increases

  Rate of photosynthesis increases
• Carbon dioxide concentration is the limiting factor


  Rate of photosynthesis is limited by carbon dioxide concentration
• Temperature increases

  Rate of photosynthesis increases
• Temperature is the limiting factor

  Rate of photosynthesis is limited by temperature
• Enzymes in leaf start to denature

  Rate of photosynthesis falls
• Greenhouses

  • Farmers use them to increase the rate of photosynthesis
  • Provide extra light and heat
  • Add extra carbon dioxide
• The extra cost of using greenhouses has to be justified by the increase in crop yield
• Energy is really important in biology for example we need energy for movement, humans and other mammals need energy to keep warm and we need energy for chemical reactions to build larger molecules for example proteins are made by chemically joining amino acids
• Respiration

  A process that supplies the energy we need, it is an exothermic reaction because it releases energy and it takes place continually in all living cells
• Aerobic respiration

  Glucose is reacted with oxygen gas, this produces carbon dioxide and water and it releases energy
• Aerobic respiration

  Releases a great deal of energy because the glucose molecule has been fully oxidized
• Glucose

  Oxygen
• Carbon dioxide

  Water
• Anaerobic respiration in muscles

  Glucose is converted to lactic acid