Fundamentals of Cellular Energy and Metabolism: Processes, Pathways, and Principles

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Fundamentals of Cellular Energy and Metabolism: Processes, Pathways, andPrinciplesbiosynthesisthe building up of biomolecules or biological structures within aliving cell; a process that requries energyenergy of concentrationthe work of moving molecules or ions against a concentrationgradient, that is, moving them from where they arelessconcentrated to where they are already more concentratedelectrical potentiala difference in charge across a membrane based on a differencein the concentration of positive and/or negative ions across themembraneCathedrals and cells both requireenergy for their constructionEnergy is the ability to make specific changeoccur within a cellEnergy is needed within cells for biosynthesis, movement,concentration of substances, generation ofelectrical potentials, and heatThegeneration of cellular energy isa unified process across the living worldEnergythe ability to make specific changes occurEnergy is freely convertible from one form to another, butenergy can never be created or destroyed in normalprocessIn all energy conversions in living systems, someo f the energygivenoff fails to be conserved as useful energy. it is lost as heatEnergy flows from the sun into the chemical reactionpathways of living things and ends up as heat

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chemical reactiona process in which bonds are broken in one kind ofmolecule (thereactant) and new bonds are formed to produce a product;energy change accompanies any chemical reactionreactantan initial substance that absorbs energy and enters into achemical reaction in which it is changed in structureproducta substance that is formed during a chemical reactionexergonicdescriptive of a chemical reaction in which free energy is givenoff; a spontaneous reactionendergonicdescriptive of a chemical reaction in which free energy must beadded in order to get the reaction to take placeIn chemical reactions, energy changes occurwhen covalent bonds in reactant molecules are broken and newbonds in product molecules are formedIfmore energy is required to break old bonds than is given offwhen new bonds form, thereaction is endergonicIf less energy is required to break old bonds than is given offwhen new bonds form, the reaction isexergonicChemical reactions arereversible. The direction in which thereaction runsdepends on the relative concentrations of reactants and productsalready in placeA chemical reaction will never begin unless there is enoughenergy present to beginbreaking bonds inreactant molecules. This amount of energy istermed the activation energyenzyme

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a type of protein molecule that serves as an organic catalist insolution. It reproducibly converts one specific sort of moleculeinto another-a specific reactant into its productactive sitea precise three-dimensional space within the structure of anenzyme where a sepcific reactant or reactants selectively bindand are there coverted to a product or productsMost chemical reactions in nature do not proceed at anysignificant rate becauseof the amount of energy present is less than the activation energyfor these reactionsAn enzyme binds to a specific reactant when the reactantdiffuses intothe enzyme's active siteEnzymes lower the activationenergy hill for specificchemical reactions, enabling them to proceed at significant ratesat low cellular temperaturesActivation energy for a reaction is lowered when the bond inthe reactant that initally needsbreaking is stressed in some way bythe active site of an enzyme.The existence of many kinds of enzymes in cell allowsmolecules to be transormed in orderly ways withincells, slowly generating useful free energy and useful structuresmetabolic pathwaya series of chemicalreactions in a sequence in which the productof one reaction is the reactant of the next reactionallosteric sitea three-dimensional groove, poscket, or surface on or within anenzyme molecule; when a specifically shaped regulatorysubstance binds the site, the enzyme's active site is alteredstructurallyfeedback inhibitiona form of rate regulation in metobolic pathways in which theproduct of some late reaction in the pathway controls the rate ofcatalysis by an enzyme earlier in the pathway

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