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)
The full range of radiation is called
the electro-magnetic spectrum
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!
Trapping Sunlight in an electron
What is source of H for glucose?
What remains when H is taken?
Light
energy
Carbon
dioxide
Water
Photosynthesis
Glucose
Oxygen
gas
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)