From owner-metabolic-reg@net.bio.net Sun Jan 09 22:00:00 1994 Path: biosci!daresbury!not-for-mail From: "" Newsgroups: bionet.metabolic-reg Subject: Re: photosynthesis, exo or endo Date: 10 Jan 1994 13:52:11 -0000 Lines: 42 Sender: daemon@mserv1.dl.ac.uk Distribution: bionet Message-ID: <2grmib$lr@mserv1.dl.ac.uk> Original-To: btk-mca@net.bio.net In <9401072317.AA26668@net.bio.net> mroussel@alchemy.chem.utoronto.ca (Marc Roussel) writes: > I'm having trouble imagining a setup in which this would be a >problem, regardless of the amount of heat evolved. Perhaps you could >explain what a "bio-reactor" is. Photosynthetic organisms need access >to light and that limits how densely they can be packed in the optical >path, with obvious implications for heat dissipation. (Photosynthetic >organisms have two basic choices: (1) cover the surface completely but >not very deeply or (2) disperse through the medium at a low density. In >both cases, heat dissipation should be facile.) > > Marc R. Roussel > mroussel@alchemy.chem.utoronto.ca A "bio-reactor" could be a large stirred tank containing, as an example, algae. t The tank is well stirred, sparged with some CO2 and has light sources (possibly immersed ones, so that moderate optical densities will not cut growth too badly. Most of the light energy will be dissipated as heat, however a portion of it will go into photosynthesis. Now the question: for each photon entering photosynthesis: is some of the energy of the photosynthetic photon lost as heat due to inefficiencies, or does the set of chemical reactions "catalyzed" by the photon require thermal energy in addition to the photon's energy? To put into an equation, do we have photon + substrate -> product + heat or photon + heat -> product ? Maybe the amount of heat one way or another is not enough to be of practically significance, but I find it surprising that no-one has been able to say which of these two is occuring. So ... WHO STARTED THIS? Paul schlosser@beta.ciit.org .