Photosynthesis Process which changed a planet
“Goals” of Photosynthesis • To trap sunlight (radiant energy) • To produce glucose (photons converted to chemical energy) • Accidental Event:Making Oxygen Gas!! (02)
SUMMARY OF KEY CONCEPTS • Overall Equation for Photosynthesis Light energy Photosynthesis Carbon dioxide Water Glucose Oxygen gas Visual Summary 7.1
Question: • Where does the plant get the carbon atoms to make glucose?
Question • How did cellular respiration release the stored energy of glucose? • Taxi-cabs stripped off high energy electrons (H atoms) from glucose and sent to the ETC
Question • How does photosynthesis put energy into glucose? • It takes low energy electrons (H atoms) from water, and “excite” the electrons with photons of light! • H atom + photon High E electron!
What is source of H for glucose?What remains when H is taken? Light energy Photo-synthesis Oxygen gas Glucose Carbon dioxide Water Unnumbered Figure 7.1
How do plants make oxygen? • ANSWER:
Why was oxygen production on Earth important? • Original atmosphere was anaerobic • First life forms were anaerobic(3.5 bya)
Why was oxygen production on Earth important? • Cyanobacteria “invented” photosynthesis • Oxygen build-up (about 2 bya) • Poisoned some of original life forms(First “pollution” crisis!) • Gave eukaryotes an advantage (They could do aerobic cellular respiration) • Complex organisms (P,A,F) now possible with aerobic cellular respiration • Terrestrial life possible with formation of the ozone layer (03)