Photosynthesis (re:carbonate buffer & equilibria)
[detailed discussion ommitted]
>So, what do submersed plants (and algae) use for photosynthesis? What
>crosses which membranes where? Anybody know?
Oh, it's been a long time, and you probably already know most of this, but I'll
The short of it is:
Inside the chloroplasts:
Light + H2O -> 2(H2) + O2
6(CO2) + (6H2) -> C6H12O6 + 3(O2)
From there, the C6H12O6 (glucose) is converted to sucrose for storage, or
further combined to form a starch. Starches are the primary component of plant
Where do the phosphates come in? The above reactions occur within a set of
steps that involve catalysts and other chemicals. One form of plant and animal
temporary energy storage is adenosine triphosphate (a nuclear peptide -
phosphate compound). Phosphates are required for energy conversion and are
also a component of cell membranes (not to be confused with cell walls).
Cellular and nuclear membranes are made up of phospho-lipid bilayers. A
phospho-lipid is basically a complex hydrocarbon (or hydroxycarbon) attached at
one end to a phosphate. This makes the molecule hydrophobic at one end (the
covalent, hydrocarbon end) and hydrophilic on the other end (the ionic,
The hydrophobic properties of phospho-lipids tend to make them congregate
around hydrophobic particles, making a phospho-lipid shell which is hydrophilic
and therefore, will mix with water. This is the reason phospholipids make such
good detergents, they surround and suspend dirt and grease particles in the
A phospho-lipid bilayer (PLB) stacks phospholipids end to end such that the
hydrophobic lipids are in contact with one another and the hydrophilic
phosphates are in contact with the water media. The following is a diagram
to attempt a graphic depiction.
O = Phosphate
| = lipid
Plant and animal cell and nuclear membranes are composed PLBs, with one side
exposed to the outer world and the other side exposed to the inner workings of
the cell. These membranes are semi-permeable: Smaller molecules with certain
properties can get through while others can't. (BTW, proteins are exported
through the membranes via ports in the membrane (I think they're called
ribosomes, but it's really been too long).
Animals and bacteria require and use more phosphates than plants because plants
use cell walls for a portion of their structure. Cell walls are made up of
starches (highly interwoven complex sugars).
Cyanobacteria go nuts in high phosphate environments because they don't have
cell walls (if I remember correctly). They use cell membranes in the same
fashion as bacteria and animals. Since they photosynthesize to make energy,
instead of processing environmental nutrients, and since they only need to
produce amino acids to replicate, they only need phosphates to expand their
cellular membranes for the next replication.
cyanobacteria + NO3- + PO4- + H2O + CO2 + light -> more cyanobacteria
Other factors can be added to decrease the blue algae, but if they aren't
continuously maintained, you get lots of blue algae.
As I stated a couple of times before, I haven't studied this in a long while,
so portions, or the entirety of this article might be in error.
David W. Webb
dwebb at ti_com
Which way did they go?
How many of them were there?
How fast were they going?
I must find them!
I am their LEADER!!!