From owner-metabolic-reg@net.bio.net Wed Jan 05 22:00:00 1994 Newsgroups: bionet.metabolic-reg Path: biosci!daresbury!doc.ic.ac.uk!warwick!pipex!uunet!europa.eng.gtefsd.com!howland.reston.ans.net!torn!utnut!alchemy.chem.utoronto.ca!mroussel From: mroussel@alchemy.chem.utoronto.ca (Marc Roussel) Subject: Re: Photosynthesis: exothermic or endothermic? Message-ID: <1994Jan6.172010.13852@alchemy.chem.utoronto.ca> Date: Thu, 6 Jan 1994 17:20:10 GMT Distribution: bionet References: <2ghd1k$4iv@mserv1.dl.ac.uk> Organization: Department of Chemistry, University of Toronto Lines: 18 In article <2ghd1k$4iv@mserv1.dl.ac.uk> "" writes: >So, what is the real question here: does photosynthesis remove energy from >the universe? (probably yes) or, does photosynthesis remove heat from the >surrounding medium (cytosol and/or the air arround the plant - I would guess >not). Ever since this discussion started, I've been trying to decide why we should care whether or not photosynthesis removes heat from its surroundings. Heat isn't a state function, so it seems a little odd to worry about it; change the conditions of the reaction (but not the starting and finishing states), and the amount of heat taken in or given out changes. Perhaps someone can then tell me why we should care about the form of energy involved in photosynthesis. We can all agree that photosynthesis is endoergic (Delta U > 0, where U is the internal energy). Does anything else really matter? Marc R. Roussel mroussel@alchemy.chem.utoronto.ca .