Archaebacteria is an organism that converts the carbon dioxode to methane by a p

Question

Archaebacteria is an organism that converts the carbon dioxode to methane by a process called methanogenesis. In this process H2 is the donor of reducing equivalents and Co2 is the electron acceptor. In archabacteria,the electron transport chain can be run in reverse. In this direction, the energy in the proton gradientis used to drive the reduction of CO2 to HCOOH and ultimatley th CH4 rather than reducing power driving the formation of a proton gradient as in typical electron transport. The H2 provides the reducing equivalents that are further transferred via other electron carriers.
a. Which way are the protons flowing during reverse electron transport chain? From the acidic outside to the basic inside or from the basic inside to the acidic outside?

b. During the normal electron transport chain which way are the protons floeing? From the acidic outside to the basic inside or from the basic inside to the acidic outside?
c.During the normal electron transport chain what is the trend inreduction potentials and what do the vaues mean?

Explanation / Answer

Methanogenesis is the conversion of carbon dioxide to methane. It occurs in the archaebacteria. In this process H2 is the donor of reducing equivalents and Co2 is the electron acceptor. In the process of methanogenesis the protons flow through a series of co-enzymes and co-factors. They are F430--coenzyme B--coenzyme M-- methanofuran--methanopterin. a) It is an reverse electron transport chain, in which the protons flow from acidic outside to basic inside. The flown protons are utilized by the carbon to form CH4. b) In the case of normal electron transport chain the protons flow through Dehydrogenase--quinone--bc1---cytochrome In this case the protons are flow from basic inside to the acidic outside, and the protons released are utilised in the formation of ATP. c) Reduction potentials the free energy change required to drive the proton transport. In the electron transport chain the redox potential of the acceptor must be more positive than the redox potential of the donor.

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