Photosynthesis Activates Plasma Membrane H+-ATPase …
ATP Synthase (FoF1-complex): Detailed information …
In the absence of transmembrane pH difference equals the transmembraneelectrical potential difference and can be directly measured by severalexperimental techniques (i.e. permeate ion distribution,potential-sensitive dyes, electrochromic carotenoid bandshift, etc.).Each pH unit of the transmembrane pH gradient corresponds to 59 mVof .
For most biological membranes engaged in ATP synthesis the value lies between 120 and 200mV ( between 11.6 and19.3 kJ mol-1).
How can ATP synthase in photosynthesis be ..
A water mill is a good analogy: the difference between the water levelsbefore and after the dam provides potential energy; downhill water flowrotates thewheel; the rotation is used to perform some work (ATP synthesis in ourcase).
Respiration And Photosynthesis Cycle Biology Essay
To make a long story short, the primary function of ATP synthase in most organisms is ATP synthesis. Hence the name. However, in some cases the reverse reaction, i.e. transmembrane proton pumpingpowered by ATP hydrolysis is more important. A typical example: anaerobic bacteria produce ATP byfermentation, and ATP synthase uses ATP to generate protonmotive force necessary for ion transportand flagella motility.
Many bacteria can live both from fermentation and respiration or photosynthesis. In such case ATP synthasefunctions in both ways.
An important issue is to control ATP-driven proton pumping activity of ATP synthase in order to avoid wasteful ATP hydrolysis under conditions when no protonmotive force can be generated (e.g. leakydamaged membrane, uncoupler present, etc.). In such case ATP hydrolysis becomes a problem,because it can quickly exchaust the intecellular ATP pool. To avoid this situation,all ATP synthases are equipped with regulatory mechanisms that suppress the ATPaseactivity if no protonmotive force is present. The degree of ATP hydrolysis inhibitiondepend on the organism. In plants (in chloroplasts), where it is necessary to preserveATP pool through the whole night, the inhibition is very strong: the enzyme hardly has anyATPase activity. In contrast, in anaerobic bacteria where ATP synhase is the maingenerator of protonmotive force, such inhibition is very weak. Mitochondrial ATP synthase is somewhereinbetween.
IB Biology: Photosynthesis And Cellular Respiration
We are grateful to Prof. J Cardenas (Dept de Bioquimica y Biologia Moleculary Fisiologia, University of Cordoba, Spain) and Prof. J.V. Moroney (Dept of Botany, Louisiana State University, USA) for critically reading the manuscript. We are also grateful to Gunilla Malmberg for expert assistance in the measurements of ATP/ADP ratios and Dr. C. Santos (The University of Cordoba, Spain) for skiful secretarial assistance. This work was supported by the Swedish Natural Research Council, Seth M. Kempes Memorial foundation and the Swedish Institute.