Biochemistry-Bioenergetics/metabolism

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Coupled Reaction

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Two chemical reactions in which the release of energy and/or the products of one reaction are used by the other

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Metabolism

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The totality of complex chemical activities that characterize living systems consisting of CATABOLIC pathways to provide free energy and precursors for the synthesis of biomolecules via ANABOLIC pathways

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Catabolism

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Is mainly defined as the step by step degradation of complex molecules to simpler ones which is coupled to the synthesis of ATP either directly or indirectly by the formation of reduced progenitors (eg. NADH for oxidative phosphorylation)

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Anabolism

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The biosynthesis of biopolymers, their precursor molecules and other necessary compounds which utilizes ATP and/or its reduced progenitors such as NADH

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Metabolic Pathway

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A given sequence of enzyme catalyzed chemical reactions in metabolism which might be either linear, branched or cyclic

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Metabolite

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Any compound that is produced by metabolism

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Primary Metabolism

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Major pathways where bulk nutrients (carbohydrates, lipids, proteins, and amino acids) are transformed in large amounts via catabolic and anabolic pathways

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Organelles

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a)organelles are membrane-bound compartments which contain a given set of enzymes (or isozymes) resulting from specific trafficking

b) Membranes provide a barrier to most solutes and are characterized by specific permeabilities mediated by membrane proteins

c)Organelles are characterized by limited metabolic functions

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Metabolon

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Intimately associated enzymes that catalyze reactions composing a given metabolic sequence

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Metabolite Channeling

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Spatially limited transfer of sequential metabolites (ie. Product of E1 is the substrate for E2 in the sequence E1-->E2, etc.) such that they do not mix with pools that are external to the Metabolon

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Direct Metabolite Transfer

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Which occurs by a collisional process between active sites of sequential enzymes in a metabolon where transfer occurs without an intervening dissociation of the metabolite

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Conducted Metabolic Transfer
(by tunnel/tracks or tether)

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by 1) diffusion of metabolites through tunnels or along external electrostatic tracks, or 2) covalent attachment of metabolites to tethers which range between different active sites

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Polyzyme

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Multiple enzyme activities in a single polypeptide chain

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Stable Multienzyme complex

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contain different polypeptide chains having different enzyme activities

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Unstable Multienzyme complex

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(such as some enzymes in glycolysis, TCA cycle, DNA/RNA/Protein synthesis, etc.) Often associated with other cellular structures such as chromatin, glycogen and membranes

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Mitchell's "Chemiosmotic" Theory for Oxidative Phosphorylation

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The free energy of the ETC is conserved by pumping H+ from the matrix to the intermembrane space which makes an electrochemical gradient of H+ across the inner membrane which, in turn, is used to synthesize ATP

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Evidence for Chemiosmotic theory

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1. OxPhos requires an intact membrane
2. This membrane is impermeable to H+
3. ETC generates a pH gradient
4. OxPhos is uncoupled by agents that collapse the H+ gradient

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Oxidative Phosphorylation (OxPhos)

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Chemical that can collapse the electrochemical gradient of H+ across the inner mitochondrial membrane