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Senanu's Bio class

Chapter 10.4 - 10.5 – C4 Photosynthesis and the Calvin Cycle

OBJECTIVE: Explain how photorespiration ‘undoes’ photosynthesis.

  1. Why does the fact that rubisco binds O2 a problem for plants?
  2. What are the products of photorespiration? Why might plants want to avoid photorespiration?
  3. Under what conditions is photorespiration a problem?
  4. Look at the cross-section of a leaf below. Describe what happens in order for photorespiration to be a problem. In particular, think about the stoma and why it may be open or closed.Cross-section of leaf

  5. In addition to carbon dioxide and oxygen, what other molecule moves through stomata? What does the plant do to reduce loss of this molecule?

    OBJECTIVE: Describe photosynthesis in C4 and CAM plants. Relate these alternative modes of photosynthesis to environmental challenges and to physiological modifications in these plants.

  1. Describe how C4 photosynthesis reduces photorespiration.
  2. When do normal (C3) plants have their stomata open?
  3. Why would this be a problem for desert plants?
  4. When do CAM plants have their stomata open?

  5. Compare C4 photosynthesis with CAM photosynthesis. How are the similar? How are they different?

    OBJECTIVE: Distinguish between the Light Reactions and the Calvin Cycle

  6. In general, what does the Calvin cycle accomplish?
  7. What are the 3 inputs to the Calvin cycle? For each, list where they come from.
  8. Write the name of the enzyme that catalyzes the first step of the Calvin cycle ________________________ (It is the most abundant enzyme on the planet!).
  9. What reaction does this enzyme catalyze?
  10. The Calvin cycle produces G3P (not glucose). Where have we seen G3P before? (Hint: look at figure 9.9).