Topic 5

• Calvin cycle


  1. Spins and spins

  2. Finishing what the light begins

  3. Plants manufacture or synthesize the food they need to stay alive
• Photosynthesis


  • Two-part process
  • Light reactions (part one)
  • Calvin cycle (part two)
• Light reactions


  1. Use radiant energy from the sun

  2. Photoelectrically generate ATP and NADPH
• Calvin cycle


  1. Uses ATP and NADPH

  2. Plus CO2

  3. To make a sugar or saccharide

  4. From which the plant's food is derived
• The Calvin cycle takes place last in the stroma of the chloroplast, the fluid-filled matrix that's contained outside the thylakoid membrane
• RuBP


  Starting compound which contains five carbon atoms in its chain
• Carbon fixation


  1. RuBP binds to CO2

  2. Rubisco enzyme helps CO2 and RuBP bind
• Unstable six carbon compound

  Splits in half and generates two PGAs or phosphoglycerates
• PGA reduction


  1. ATP gives phosphate to PGAs

  2. Produces bisphosphoglycerates

  3. NADPH reduces bisphosphoglycerates

  4. Produces phosphoglyceraldehydes (PGALs or G3P)
• G3P


  Glyceraldehyde 3 phosphate
• Glucose synthesis


  1. Two G3Ps bind to form glucose (C6H12O6)

  2. Calvin cycle spins 6 times to obtain 12 G3Ps (36 carbons) for glucose
• RuBP regeneration


  10 G3Ps are recycled and rearranged enzymatically to regenerate RuBP
• Photosynthesis, parts one and two, help make G3P, which plants can use to make glucose and other organic molecules
• The Calvin cycle spins and spins, finishing what the light begins