MODULE 5

• Photosynthesis


  The food-making process which converts light energy from the sun into chemical energy in food
• Photosynthesis


  • Requires molecules of water and carbon dioxide in the presence of sunlight and chlorophyll to produce the food (glucose) and release the by-product oxygen
  • Organisms which contain chlorophyll like algae and plants can perform photosynthesis
• Chloroplast


  Disc shaped structures inside the plant cells that contain chlorophyll
• Thylakoids


  Disc shaped structures inside the chloroplasts that contain chlorophyll
• Granum


  Stacked thylakoids inside the chloroplast
• Leaves


  • The main area for photosynthesis
  • Contain mesophyll layers with palisade and spongy layers
  • Have stomata that allow carbon dioxide to enter and oxygen to leave
• Photosynthesis

  1. Light dependent reaction

  2. Light independent reaction (Calvin cycle)
• Light dependent reaction

  Occurs in the thylakoids of the chloroplast, requires light energy and water, produces ATP and NADPH
• Light dependent reaction

  • Involves two photosystems: PI and PII
  • Chlorophyll in photosystem II captures light energy and passes it to the P680 reaction center
  • Electrons lost from P680 and P700 are replaced by electrons from water (photolysis)
  • Movement of electrons produces ATP (photophosphorylation)
• Non-cyclic photophosphorylation


  Electrons move from photosystem II to photosystem I, producing ATP and NADPH
• Cyclic photophosphorylation


  Electrons follow a cyclic path, producing only ATP
• Light independent reaction (Calvin cycle)


  Occurs in the stroma of the chloroplasts, uses the ATP and NADPH from the light dependent reaction to produce glucose
• Calvin cycle

  1. Carbon fixation

  2. Reduction phase

  3. Carbohydrate formation

  4. Regeneration phase
• Energy to fuel chemical reactions in the Calvin cycle is provided by ATP and NADPH, which contain the energy plants have captured from sunlight
• Light-dependent reaction


  1. Electron moves from PII to PI

  2. Produces ATP and NADPH
• Cyclic photophosphorylation

  1. Electrons follow a cyclic path

  2. Produces ATP
• Events in light-dependent reaction

  • Activation of electron in chlorophylls of P680 and P700
  • Photolysis
  • Photophosphorylation: Non-cyclic and Cyclic
• Raw material


  Water
• Products


  ATP and NADPH
• Oxygen is a by-product
• Light-independent reaction (Calvin Cycle)

  1. Carbon fixation

  2. Reduction phase

  3. Carbohydrate formation

  4. Regeneration phase
• Carbon fixation


  Carbon in CO2 is fixed from inorganic to organic molecule using enzyme Rubisco
• Reduction phase


  1. carbon compound is reduced into 3-PGA using ATP and NADPH
• Carbohydrate formation

  G3P is converted into glucose, 2 G3P needed for 1 glucose
• Regeneration phase


  G3P used to make glucose and regenerate RuBP, 3 more ATP used
• Calvin Cycle uses 6 CO2 to produce 1 glucose, uses ATP and NADPH from light reaction
• Comparison of light-dependent and light-independent reactions

  • Raw materials
  • Products
  • Location
• Photosynthesis is important for the balance of nature
• Oxygen in light-dependent reaction comes from water
• Activities to help maintain oxygen-carbon dioxide balance include sorting waste, recycling, tree planting
• Photosynthesis

  1. Light-dependent

  2. Light-independent
• Activities to lessen global warming

  • 3 R's (Reduce, Reuse, Recycle)
  • Tree planting
  • Proper waste disposal
• Chlorophyll captures light energy from the sun
• Light and water are required to start light-dependent reaction
• Water is used in the production of H+, e- and O2 in photosynthesis
• Oxygen is released in the light-dependent reaction
• Carbon dioxide is not a product of photosynthesis
• ETC


  Produces 32 ATPs
• Total amount of ATP starting from Glycolysis until the last stage

  36 ATPs in organisms with mitochondria
• Oxygen-Carbon Dioxide Cycle


  Gas exchange carried out by plants and animals