Photosynthesis: Alternative Pathways Photorespiration Occurs

1
(No Transcript)
2
(No Transcript)
3
Compare and Contrast
Versus
4
Photosynthesis Alternative Pathways
5
C3 Plants

• Cool, moist environments

6
C3 Plants

• Called C3 because the 1st organic product of
  the Calvin Cycle is a 3-C molecule
  (3-phosphoglycerate)
• Rubisco catalyzes 2 reactions RuBP with CO2 or
  RuBP with O2

7
Photorespiration
8
Photorespiration

• Occurs when Rubisco binds with O2 instead of CO2
• RuBP O2 ? Phosphoglycolate 3-phosphoglycerate
• Decreases production of sugars

9
C4 Plants

• Hot, dry environments

10
C4 Plants

• Spatial separation
• Enzyme PEP carboxylase fixes CO2 into a 4-C
  compound oxaloacetate
• Unique leaf anatomy Mesophyll cells surround
  Bundle Sheath cells
• Mesophyll cells take in CO2
• Calvin Cycle occurs within Bundle Sheath only

11
C4 Plants
12
CAM Plants

• Hot, dry, arid environments

13
CAM Plants

• Crassulacean Acid Metabolism
• Temporal separation
• Night stomata open to allow in CO2
• CO2 incorporated into organic acids and stored in
  vacuoles of mesophyll cells
• Day stomata closed ? conserve H2O
• Organic acids release CO2 for Calvin cycle

14
C4 versus CAM
15
Homework

• Read pg 168-171
• Questions p172 2,4,6
• Cheat sheet for C4 and CAM plants only

16
Venn Diagram

• Read pg 179-180
• Draw a Venn Diagram comparing the similarities
  and differences between cellular respiration and
  photosynthesis.