Biochemistry and Molecular Biology - Belyasova N.A. 2002

Metabolism. Energy storage pathways
Respiration

Respiration is one of the most widespread Methods of energy conservation utilized by the majority of organisms: animals, plants, Protozoa, Fungi, aerobic, and almost all facultatively anaerobic Bacteria. During respiration, energy is conserved via Oxidative Phosphorylation; both organic and Inorganic Compounds can act as electron Donors, whereas only inorganic substances serve as electron acceptors. Compared to substrate-level phosphorylation, Oxidative phosphorylation is a far more advantageous and efficient mechanism, representing an evolutionarily advanced stage. Its defining feature is the mandatory involvement of membranes, within which the Components of the Respiratory Chain are arranged in a strictly defined sequence. The driving force behind ATP synthesis is the energy of the transmembrane proton gradient. In turn, the proton gradient is generated by electron transport through the respiratory chain components in a specific direction: from a better donor to a better acceptor.

The components of the respiratory chain (electron transport system) and The enzyme catalyzing ATP synthesis (ATP synthase) are located in Cell/30.html">The Plasma Membrane in prokaryotes, and in The inner mitochondrial membrane in eukaryotes. It is within these Organelles, as previously shown (Chapters 9, 11), that the largest amount of reducing equivalents is generated during catabolic and amphibolic processes, to be transferred to the respiratory chain via nicotinamide and flavin carriers.

The respiratory chain carries out reactions that represent a biochemical analog of hydrogen combustion. Their defining feature is the conservation of a significant portion of the released energy in the form of high-energy bonds of ATP, i.e., The conversion of Free energy into a biologically usable 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 of their functioning, and their arrangement within the membrane.