Bioenergetics

• Photosynthesis


  1. Takes place in leaves

  2. Takes place in chloroplasts

  3. Chlorophyll absorbs light

  4. Converts carbon dioxide and water into glucose and oxygen
• Photosynthesis requires light energy
• Endothermic reaction


  Reaction where energy is transferred from the environment
• How plant gets reactants for photosynthesis

  1. Carbon dioxide diffuses into leaves through stomata

  2. Water is taken up from soil by roots and transported to leaves via xylem
• Products of photosynthesis


  • Glucose is essential
  • Oxygen is also produced but not as important
• Uses of glucose


  • Cellular respiration
  • Making cellulose
  • Making starch
  • Making amino acids
  • Making oils and fats
• Plant growth rate often depends on rate of photosynthesis
• Factors affecting rate of photosynthesis are light intensity, temperature, carbon dioxide concentration, and amount of chlorophyll
• One use of glucose is to make amino acids. 

  What else do plants need to make amino acids?

  nitrate ions
• What are the main uses of glucose in plants? 

  Cellular respiration - break down the glucose to release energy 

  Make cellulose - which is used to make strong cell walls

  Make starch - which is used to store glucose for a later time

  Make amino acids - which are used to make proteins 

  Make lipids - these store the energy as fats or oils for later use
• Describe and explain how the rate of photosynthesis varies with temperature. 

  Increasing the temperature increases the rate of photosynthesis as the kinetic energy of the particles increases. The rate of photosynthesis decreases past a certain temperature as the enzyme becomes denatured
• Farmers in cooler climates often use greenhouses. These help trap the heat energy from sunlight, and so increase the temperature. They also keep out pests which could otherwise damage the plants.
• How can farmers ensure that photosynthesis takes place 24 hours a day?

  use artificial lighting
• Paraffin heaters have two benefits. As the paraffin (a type of fuel) is burned it releases lots of heat, and also lots of:


  carbon dioxide