Photosynthesis part deux: The Calvin Cycle

Chapter 6-2 pages 117-120

At right is Melvin Calvin who worked all this outBelow is Calvin who worked out Calvin Ball

Objectives

• Summarize the main events of the calvin cycle

• Describe what happens to the compounds that are made during the calvin cycle

• Distinguish between c3, c4, and CAM plants

• Summarize how the light and dark reactions work together in photosynthesis

• Explain how environmental factors affect photosynthesis

Calvin Cycle

• From photosynthesis we get ATP and NADPH

• Now we’ll 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

Carbon Fixation

• Carbon fixation is the building of biomolecules from CO2

• 3 steps of the Calvin Cycle1. 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

Calvin CycleStep 2

2 PGAs converted to another 3 Carbon molecule PGAL, in a two part process

1. PGA receives a Phosphate from ATP2. NADPH gives its H+

The ADP, NADP+, and Phosphate are reused back in the photosynthesis reaction

Calvin Cycle

Step 3

Some of the PGAL goes back to RuBP so the Cycle can continue

Other PGAL goes elsewhere to make Biomolecules

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.

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

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