Photosynthesis

What is the worst case of environmental poisoning in the history of earth?

Types of metabolism

1. Autotrophs
   1. Absorption of nutrients
   2. Photosynthesis
2. Heterotrophs
   1. Digestion
   2. Cellular Respiration
3. Metabolism in ecosystems
   1. Consumers
   2. Producers

A. Types of photosynthetic organisms

1. Plants
2. Algae
3. Bacteria

B. Where photosynthesis happens

1. Anatomy of a leaf
   • Epidermis
   • Stomata
   • Mesophyll
2. Chloroplasts
   • Thylakoid membranes
   • Stroma
3. Photosynthetic pigments absorb light
   1. Chlorophyll
   2. Carotenoids
   3. Xanthophylls

C. How photosynthesis works

1. Overview: From light to chemical energy

   6 CO₂ + 6 H₂O = 1 C₆H₁₂O₆ + 6 O₂

2. How cells store energy (Part 2)
   1. ATP
   2. electrons (reducing power)
      • NADPH
3. The light reactions
   1. Light (photon) hits pigment
   2. Electron gets "excited"
   3. Electron flows down the electron transport chain
   4. ATP is made
   5. Electrons (Hydrogens) are trapped (NADPH)
   6. Water is split
4. The dark reactions (Calvin cycle)
   1. Fixing carbon dioxide
      • Rubisco: the most common enzyme on earth!
   2. Adding Hydrogen ("Reduction")
   3. Making sugar
5. Summary: How much energy does it take?

D. Some variations on this theme

1. Bacterial photosynthesis
   • Cyanobacteria
   • Other bacteria
2. Tropical plants
   • Corn & crabgrass (C4 plants)
   • Pineapple & cactus (CAM plants)

Applications

1. Life on Earth: The worst case of environmental poisoning
2. Environmental impact of photosynthesis
   1. Primary production
   2. Oxygen production
   3. Carbon dioxide reduction
3. Global warming?