Photosynthesis part deux: The Calvin Cycle

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Photosynthesis part deux The Calvin Cycle

• Chapter 6-2 pages 117-120
• At right is Melvin Calvin who worked all this out
• Below is Calvin who worked out Calvin Ball

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Calvin Cycle

• From photosynthesis we get ATP and NADPH
• Now well use the energy from that to make
  biomolecules

• The energy from Niagra falls is used to power
  turbines so we can use electricity to do work

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Carbon Fixation

• Carbon fixation is the building of biomolecules
  from CO2
• 3 steps of the Calvin Cycle
• 1. CO2 diffuses into the stroma from the
  surrounding cytoplasm. RuBP is combined with
  CO2. The new 6 Carbon molecule splits into 2 3
  Carbon molecules called PGA

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Calvin Cycle

• Step 2
• 2 PGAs converted to another 3 Carbon molecule
  PGAL,
• in a two part process
• 1. PGA receives a Phosphate from ATP
• 2. NADPH gives its H
• The ADP, NADP, and Phosphate are reused back in
  the photosynthesis reaction

• Confused, stare at this picture, watch the lines
  seem to move. Now get back to work

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Calvin Cycle

• Step 3
• Some of the PGAL goes back to RuBP so the Cycle
  can continue
• Other PGAL goes elsewhere to make Biomolecules

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Balance sheet for Photosynthesis

• Calvin Cycle has to turn 3 times to get a PGAL
• That uses 9 ATPs and 6 NADPHs
• Now no glucose has been made yet. Cellular
  respiration is where Glucose is involved.

• The Lakers appreciate the Calvin Cycle, you
  should to.

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Alternative pathways

• C3 Plants only fix carbon through the Calvin
  Cycle
• Most plants are this, trees for example
• In hot climates plants lose water through open
  stomata so they need to keep stomata closed
• But stomata are where CO2 O2 leave and enter
  the cell

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Alternative Pathways

• C4 pathway plants put CO2 into 4 carbon
  molecules
• Corn Sugar Cane are examples
• CAM pathway plants have stomata open at night and
  closed during the day, the opposite as normal
• includes Cactus Pineapple