From owner-btk-mca@hgmp.mrc.ac.uk Mon Oct 8 15:10:43 2001 Return-Path: Received: from localhost (localhost [127.0.0.1]) by mercury.hgmp.mrc.ac.uk (Postfix) with ESMTP id F0D6217A9D for ; Mon, 8 Oct 2001 15:10:42 +0100 (BST) Received: from localhost (localhost [127.0.0.1]) by mercury.hgmp.mrc.ac.uk (Postfix) with ESMTP id 1596617A70 for ; Mon, 8 Oct 2001 15:10:36 +0100 (BST) Received: from niobium.hgmp.mrc.ac.uk (niobium [193.62.192.41]) by mercury.hgmp.mrc.ac.uk (Postfix) with ESMTP id 425F917A9D for ; Mon, 8 Oct 2001 15:10:33 +0100 (BST) Received: (from news@localhost) by niobium.hgmp.mrc.ac.uk (8.9.3+Sun/8.8.8) id PAA07013 for btk-mca-list@hgmp.mrc.ac.uk; Mon, 8 Oct 2001 15:04:55 +0100 (BST) X-Authentication-Warning: niobium.hgmp.mrc.ac.uk: news set sender to using -f From: pkuzmic@biokin.com (Petr Kuzmic) X-Newsgroups: bionet.metabolic-reg Subject: Re: delta-G of biochemical reactions Date: 8 Oct 2001 07:04:53 -0700 Organization: http://groups.google.com/ Lines: 38 Message-ID: <77754d4.0110080604.47ee92d9@posting.google.com> References: <3BB4AAA7.8790.DF1D392A@localhost> <77754d4.0110070742.6f61b8f@posting.google.com> <3BC0E343.192978FB@zonvark.wustl.edu> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Complaints-To: groups-abuse@google.com To: btk-mca@hgmp.mrc.ac.uk Sender: owner-btk-mca@hgmp.mrc.ac.uk Precedence: bulk gavin wrote in message news:<3BC0E343.192978FB@zonvark.wustl.edu>... > It's true that kinetics is important in biochemical reactions. > But the reaction must first have the > thermodynamic drive to proceed. If the Gibbs free energy > is positive (i.e. unfavorable going from > left to right), there is no amount of rate constant that can make > the reaction to go from left to right. That is true, but the phenomenon of "kinetic control" vs. "thermodynamic control" is more subtle. At issue is not a particular processes (biochemical reaction) taken in isolation, which is what you are referring to. Instead, consider two biochemical processes proceeding at the same time: A ---> B1 : dG1 A ---> B2 : dG2 It is possible that dG2 is more negative then dG1, which means at thermodynamic equilibrium you would expect more B2 than B1. Despite of this fact, under "kinetic control" (determined by the values of rate constants) the product B1 might be formed in significantly greater amount in comparison with B2. In this sense, thermodynamic considerations are misleading, not applicable to understanding what might happen in the cell. This seems to be the case with zinc trafficking. - Petr --------------------------------------------------- P e t r K u z m i c, Ph. D. * BioKin Ltd. 1652 S. Grand Ave. * Suite 337 * Pullman, WA 99163 509.334.4131 * 509.332.3493 fax * http://www.biokin.com .