Producers and Consumers Autotrophs (self-feeders): Make their own organic matter from inorganic nutrients. Heterotrophs (other-feeders): Organisms that cannot make organic molecules from inorganic ones. 1

Energy Flow and Chemical Cycling in the Biosphere Sunlight energy enters ecosystem CO2 (Carbon dioxide) C6H12O6 (Glucose) Photosynthesis + + O2 (Oxygen) H2O (water) Cellular respiration ATP drives cellular work Heat energy exits ecosystem 2

Photosynthesis Photosynthesis: Is used by plants, some protists, and some bacteria Transforms light energy into chemical energy Uses carbon dioxide and water as starting materials Light energy 6 CO2 6 O2 6 H2O C6H12O6 Photo- synthesis Carbon dioxide Water Glucose Oxygen gas 3

Photosynthetic Protists Photosynthetic Bacteria Photosynthesis Organisms that use photosynthesis are: Photosynthetic autotrophs The producers for most ecosystems PHOTOSYNTHETIC AUTOTROPHS Plants (mostly on land) Photosynthetic Protists (aquatic) Photosynthetic Bacteria (aquatic) LM Forest plants Kelp, a large alga Micrograph of cyanobacteria 4

found b/w lower and upper epidermis Photosynthesis found b/w lower and upper epidermis 5

Photosynthesis H2O CO2 Light Calvin Light cycle reactions O2 NADP+ ADP Chloroplast NADP+ ADP P Calvin cycle Light reactions ATP NADPH O2 Sugar (C6H12O6) 6

*Photons are absorbed by pigment molecules Photosynthesis *photon *Photons are absorbed by pigment molecules

Why Green? Light Reflected light Chloroplast Absorbed light Transmitted light 8

Light-harvesting complexes of the thylakoid membrane

Electron Flow

Organization of light reaction machinery

Chemiosmosis: A Comparison

Calvin cycle (Carbon Fixation)

Photosynthesis

Alternative Pathways C4 Pathway (example: sugarcane) CAM Pathway ALTERNATIVE PHOTOSYNTHETIC PATHWAYS C4 Pathway (example: sugarcane) CAM Pathway (example: pineapple) Cell type 1 CO2 CO2 Night Four-carbon compound Four-carbon compound CO2 CO2 Cell type 2 Calvin cycle Calvin cycle Sugar Sugar Day C4 plant CAM plant 15