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By D. Rao Sanadi

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Critical Phenomena in Loop Models

While with regards to a continual section transition, many actual platforms can usefully be mapped to ensembles of fluctuating loops, which would characterize for instance polymer jewelry, or line defects in a lattice magnet, or worldlines of quantum debris. 'Loop versions' offer a unifying geometric language for difficulties of this type.

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75, 75 % of the bacteriorhodopsin molecules p u m p inward and 25 % p u m p o u t w a r d ; here η is a positive integer, probably 1). Variations in α change the proportionality constant relating and Afin only between η · and —n-L^, 3. Light as a Thermodynamic Force It is not a priori clear how the absorption of p h o t o n s by bacteriorhodopsin must be translated into thermodynamic variables. , 1979) we have adopted the following approach. , the wavelength of the incident light, though for a given c h r o m o p h o r e such a dependence would be Hmited owing to the dis­ crete nature of light absorption).

This treatment of the d a t a makes implicit assumptions a b o u t the value of the stoichiometric constants Πη and tin and about the size of Li,. T h e fact that a good fit of the data with a straight line was obtained, lends some support to the validity of these assumptions. In these experiments some variation in Ao occurred, which m a d e it necessary to m a k e the plot as described, not as a plot of Jq against Ap. F r o m the form of the equation it is clear that at constant Aq increasing leaks of the mitochondrial m e m b r a n e for p r o t o n s (LH) will cause an increase 54 Η .

Just as in the case of mitochondria, it can be shown that in chromatophores (where the active site for A T P synthesis is located on the external surface of the vesicles) the relation (-Ap/Aßnr = nf, (102) should hold. Initial reports by Casadio et al (1974) indicated a very high value for A/ÍH , so that the calculated stoichiometric n u m b e r was smaller than 2. However, later experiments have shed some d o u b t on the validity of the use of the carotenoid shift as an indicator for bulk A ^ across the m e m b r a n e (although it may register a local gradient close to the electrontransfer chain and ATPase).

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