Biochemistry and Molecular Biology - Belyasova N.A. 2002

Metabolism. Processes Leading to Energy Storage
Respiration

Respiration is one of the most widespread energy storage mechanisms utilized by the vast majority of organisms, including animals, plants, protists, Fungi, aerobes, and almost all facultatively anaerobic Bacteria. During respiration, energy is conserved via Oxidative Phosphorylation, where electron Donors can be either organic or Inorganic Compounds, whereas electron acceptors are strictly inorganic. Compared to substrate-level phosphorylation, Oxidative phosphorylation is a far more advantageous and efficient mechanism that represents a higher evolutionary milestone. Its defining characteristic is the obligatory involvement of membranes, within which the Components of the Respiratory Chain are arranged in a strictly ordered sequence. The driving force for ATP synthesis is the energy of the proton gradient across the membrane. In turn, this proton gradient is generated by the directional transfer of electrons along the respiratory chain components: from the strongest donor to the strongest acceptor.

The components of the respiratory chain (The electron transport system) and the enzyme that catalyzes ATP synthesis (ATP synthase) are located in Cell/30.html">The Plasma Membrane in prokaryotes, and in The inner mitochondrial membrane in eukaryotes. As discussed previously (Chapters 9 and 11), it is within these Organelles that catabolic and amphibolic processes yield the largest amounts of reducing equivalents, which are subsequently fed into the respiratory chain via nicotinamide and flavin carriers.

The respiratory chain carries out reactions that serve as a biochemical analogue of hydrogen combustion. Their distinct feature is the conservation of a significant portion of the released energy in the form of high-energy ATP bonds, thereby converting Free energy into a biologically accessible form. Only a small fraction of The energy released during respiration is dissipated as heat.

To understand the Mechanism of Oxidative phosphorylation, it is first necessary to characterize the components of the respiratory chain, the principles governing their function, and their spatial Organization within the membrane.