hrvatski

Bioenergetika - rad membranskih proteina

Bioenergetics, as the science about cellular energy transduction, is mainly concerned with the problem as to how respiration and photosynthesis lead to ATP synthesis. Through evolution cells have learned to use external free-energy sources for charge separation and for the creation of very strong electric fields. The chemiosmotic theory explains in principle how protonmotive force is created by membrane proton pumps and how proton back-current can be converted into a synthesis of ATP molecules. The author discusses the molecular details of the structure and function of integral membrane proteins acting as proton pumps or ion channels. Some antimicrobial peptides are able to diminish the membrane potential part of the protonmotive force. Experiments have been described in which the transmembrane potential of rat liver mitochondria and cytochrome c oxidase vesicles has been titrated with polypeptide antibiotics of the magainin type. The author's algorithm, available as the web server http://pref.etfos.hr, is used to predict the conformation and to locate membrane domains in the sequence of P-glycoprotein, cystic fibrosis conductance regulator, ATPase, glutamate receptors, nicotinic acetylcholine receptor and voltage-dependent potassium channels from brain. Hypothetical phosphor-code for memory formation in the brain is associated with specific receptors and high level of free-energy transduction in corresponding brain regions. It is pointed out that, in general, biological energy conversion is a very intensive process which speeds up the thermodynamic evolution of a closed system and maintains an open system very far from a state of equilibrium. Thermodynamic and biological evolution are not in opposition one to another, because thermodynamic evolution makes possible biological evolution and biological evolution speeds up thermodynamic evolution. Recent increases in planetary entropy production due to human activity will lead in due time to drastic climatic changes and biosphere evolution toward new steady state less suitable for Homo sapiens. Instructions as to how to prepare ion-selective electrodes and cytochrome c oxidase vesicles are included in appendixes, where many useful addresses for WWW molecular biology sites can be found too. A total of 532 recent references are cited in the body of the text and 62 pictures are also included.

bioenergetika; neravnotežni procesi; membrane; membranski proteini

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