P/S

• Life on earth depends on energy from the sun
• Photosynthesis


  Synthesis using light

  
• Photosynthesis is responsible for almost all the planet's energy resources

  
• Photosynthesis

  6CO2 + 6H2O → C6H12O6 + 6O2

  
• Chloroplasts


  The site of photosynthesis

  
• Chloroplasts


  • Contain thylakoid membrane
  • Contain stroma
  • Have three membranes (outer, inner, thylakoid)
• Thylakoid membrane


  Where light reactions take place
• Stroma


  Where carbon fixation occurs
• Light reactions


  1. Photosystems capture light energy

  2. Chlorophyll absorbs light energy

  3. Light energy converted to high energy electrons

  4. High energy electrons move through photosynthetic electron transport chain

  
• Photosynthetic electron transport chain

  • Transfers high energy electrons
  • Produces ATP and NADPH

  
• Calvin cycle (carbon fixation)

  1. Fixation: 3 x 5 carbon molecules + 3 x CO2 → 3 x 6 carbon molecules (unstable) → 6 x 3 carbon molecules

  2. Reduction: 6 x 3 carbon molecules converted into a different type of 3 carbon molecule

  3. Regeneration: 5 x 3 carbon molecules converted to 3 x 5 carbon molecules

  4. 1 x 3 carbon molecule leaves the cycle
• The output of the Calvin cycle is a 3 carbon sugar that, when combined with another 3 carbon sugar, is converted to glucose
• ATP and NADPH produced in the light reactions are used to fix CO2 and produce carbohydrate
• Plant cells break down glucose from photosynthesis in the mitochondria using cellular respiration
• Inputs of photosynthesis


  • Light
  • Water
  • CO2

  
• Outputs of photosynthesis


  • Glucose
  • Oxygen
• Almost all glucose on Earth has directly or indirectly come from photosynthesis
• Both plants and animals breakdown glucose in cellular respiration to generate ATP
• Animals must have an external source of glucose
• ATP synthase


  Responsible for ATP generation in both respiration and photosynthesis

  
• ATP synthase requires a proton gradient across a membrane in both the chloroplast and mitochondrion
• Mitochondria and chloroplasts

  • Both contain DNA, ribosomes and are able to make some proteins
  • Both have an outer and inner membrane (chloroplasts have a third membrane system too)
• Mitochondria and chloroplasts originated through endosymbiosis
• The light-dependent reactions take place in the thylakoid membranes of the chloroplasts.
• Water molecules are split during the light-dependent reactions, releasing oxygen as a byproduct.
• The light-dependent reactions occur in the thylakoid membranes, while the Calvin cycle occurs in the stroma.
• During the light-dependent reactions, light energy is absorbed by chlorophyll and converted into chemical energy in the form of ATP and NADPH.
• Photosystem II uses water as its electron donor.
• ATP synthase converts ADP and Pi into ATP using the proton gradient generated by photosynthesis.
• NADP+ is reduced to NADPH during photosynthesis.
• Light-independent reactions (Calvin Cycle) use CO2, ATP, and NADPH to produce glucose.