Lecture 3 chemoautotrophes (prolaryotes only)
5 lineages of photosynthetic bacteria – produce sulfur beds mostly, but cyanobacteria are
the only ones who exhibit oxygenic photosynthesis
Prokaryotes very evolutionarily labile, lots of variation happening at cell level, metabolic
Green is signature of photosynthesis in plants
Range in the visible light where it’s not overwhelming for chemistry but enough energy to
be useful – leaves look green because absorbing whole spectrum, but absorb a little less green
so it’s reflected into our eyes. Also occurs in “green bark” – ie eucalyptus leaves
What is the source of plant mass?
o Mass coming from air, from CO2, Carbon – water being used for oxidizing
o Leaves have 98% relative humidity, and air is only 30 to 80%, so they need a
constant source of water, through the soil. Loses entire water content every twenty
Where is photosynthesis happening?
o Palisade cells have chloroplasts, actually do the carbon fixation – pressed against
cell surface because cell transfer less effective in liquid than in air
o What are chloroplasts? Derive from cyanobacteria, which was swallowed up by a
cell which did not fully digest it
o Most of plant body is heterotrophic and relies on leaves and layer in bark to feed it.
o Endosymbiosis is kind of a common event.
o CO2 capture by RuBisCO preadates cyanobacterial contribtion of using water to
capture electrons, but most ancient part is ATP and NADPH, which were derived
o Energy from the sun and electrons from water transferred together via ATP and
NADPH to reduce CO2, allowing it to be used to build carbohydrate molecules.
o Light reaction (lumen) and dark reaction (but doesn’t occur in dark – happens at
same time in adjacent spaces)
o Metabolism occurs across membranes
o Stroma is space outside membranes. Protons pumped into acidified lumen space,
then pumped into ATP synthase to produce ATP