Campbell et al., Chapter 10

Photoautotrophs (chemoautotrophs barely significant)
6 CO2 + 6 H2O --> C6H12O6 + 6 O2
6 CO2 + 12H2O --> C6H12O6 + 6 O2 + 6H2O actually
light for energy, corn photosynthesis up with greater light

Spectrum light comes in waves (also photons)
X,Gamma, UV, "visible," IR, radio, radar
Visible: 400 -700 nm (10-9), mm wavelength
short: ionize (damage), middle: excite electrons (reactions), long: vibrate molecules (heat, waste)
Sun cut-off 300 nm because of ozone (O3), peak at visible wavelengths, tail way out to long wavelengths
DNA 260 nm (absorption peak and possible damage)
Protein 280 nm (absorption peak and possible damage)
terrestrial life could only evolve after ozone
evolution of "vision" to use the light that is present:
also "near" UV (UVA, 300-400 nm), visible, IR (snakes).
Plants also use visible light

TRANSPARENCY (Fig. 10.7) "the process of science" absorption spectrum
white light split into spectrum and monochromatic wavelength picked through slit
Here is my monochromator with yellow light feeding through the slit

TRANSPARENCY (Fig. 10.8) Pigments
Chlorophyll absorb MOSTLY long wavelengths
Antenna pigments (including carotenoids) absorb shorter wavelengths and transfer energy to chlorophylls
TRANSPARENCY (Fig. 10.6) Leaves are green because they absorb all but green light
Fall colors are because carotenoids remain after chlorophyll is lost
In summary, leaves get most of the ight available

Must increase area. Problems with water loss (considering area of leaves for light capture)
Stoma close at night (except in CAM (crassulacian acid metabolism)
plants, desert succulants, store CO2 in organic acids
and close if too hot
light and low CO2 cause stomata to open

Chloroplast TRANSPARANCY (Fig. 10.4)
-- grana stacks
-- stroma (dark reactions) fluid matrix
-- thykaloid space (light reactions)
---------(lamellae) fret connect stacks
intracellular symbiote theory for chloroplasts and mitochondria

Light reactions
H2O used
H2O split to electrons, H+, O
electron transport gives bits of energy to molecules transporting electrons
electron donors, acceptors, transport
"Photosystem" = several hundred "antenna" + trap chlorophyll a
electron and light to PSII (680 nm chlorophyll)
ADP + P --> ATP
then electron to PSI 700 nm chlorophyll
2 H+ + NADP+ --> NADPH (reduction) (O2 used or put out)
O2 not put into carbohydrate TRANSPARENCY (Fig. 10.3)
at night, use O2, put out CO2
in grana of chloroplasts

ATP + NADPH to dark reactions (light independent) CO2 used
12 NADPH --> 12 NADP (give H to carbohydrate)
18 ATP --> 18 ADP + 18 P (give energy)
CO2 fixation and reduction C and O2 to carbohydrate
(not O of H2O, covered above)
Calvin cycle, 1961 Nobel, 14C,
add CO2 to "rubisco"
(glyceraldehyde 3-phosphate 3 carbon sugar made) -> sugar
C3 (3-phosphoglyceric acid after CO2 added to rubisco
TRANSPARENCY (Fig. 10.18) C4 sugar cane, crab grass (for hot and dry)
(a 4-carbon compound, anatomy of leaf different)
ADP, P, and NADP to light reactions

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