Photosynthesis and Plants

1. Photosynthesis and Plants • 6CO2 + 6H2O + sunlight C6H12O6 + 6O2 • Epidermis with cuticle • palisade mesophyll – parenchymal cells – primary sites of photosynthesis • Spongy mesophyll – CO2 exchange • Vascular bundles – xylem and phloem for water and sugar transport • Lower epidermis with stomata and guard cells

2. Cross section of leaf

3. Chloroplast anatomy

4. Reactions of Photosynthesis • Light reactions • Dark reactions – Calvin cycle

5. Light Reaction • Photons strike thylakoid membrane activating chlorophyll and electrons from water • Excited electrons move down electron transport chain • ATP and NADPH are produced

6. Antenna complex • Chlorophyll a, b, and carotenoids • Pigments gather light • Reaction ctr. “excites” electrons • light reactions

7. Non-cyclic Photophosphorylation

8. Cyclic Photophosphorylation • Simple way to create ATP • Photons absorbed in PS I (700) • Electrons excited • Passed down cytochrome ETS • ATP generated, electrons passed back to PS I • No NADPH • No photolysis

9. Dark Reactions • Use ATP, CO2, and NADPH to create sugars • Calvin cycle

10. Photorespiration • Rubisco reduces the CO2 concentration then starts to bind oxygen • C4 alternative – CO2 combines with PEP to form oxaloacetate (4 Carbon sugar) • PEP carboxylase (enzyme that catalyzes C4 rxn.) has high affinity for CO2. • Oxaloacetate converts to malate and shuttled to bundle sheath cells • CO2 released for use in Calvin cycle

11. C4 photosynthesis

12. CAM photosynthesis