ATP: adenosine triphosphateOrganisms classified according to energy and carbon sourcePhototrophs: energy from sunlightAutotrophs: carbon from CO2 (plants)Heterotrophs: carbon from organic compoundsChemotrophs: energy from chemical compoundsAutotrophs: carbon from CO2Heterotrophs: carbon from organic compounds (animals)Metabolism: chemical reactions that convert molecules into other molecules and transfer energy to living organismsCatabolism: break down molecules into smaller units, produces ATPMacromolecules: carbohydrates, proteins, fats, nucleic acidsAnabolism: build molecules from smaller units and requires ATPSubunits: sugars, amino acids, fatty acids, nucleotidesChemical energy is a form of potential energyC-C and C-H bonds electrons far away from atoms, store chemical potential energyCarbohydrates, lipids and proteins fuel moleculesATP is cell’s energy currencyChemical energy of ATP is held in phosphate bondsAdenine + Ribose Adenosine+ 1 phosphate Adenosine 5’-monophosphate (AMP)+2 phosphates Adenosine 5’-diphosphate (ADP)+3 phosphates Adenosine 5’-triphosphate (ATP)First Law of Thermodynamics: energy is conservedEnergy changes from one form to another, total amount always stays the sameSecond Law of Thermodynamics: disorder tends to increaseEnergy available to do work decreases (disorder increase)Energy loss due to entropy, often in the form of heatChemical ReactionsGibbs free energy (G) – amount of energy available to do work∆G is positive + products have more free energy than reactants, net input of energy is required to drive reactionNot Spontaneous (requires energy): endergonicAnabolic reactions have +∆G, require ATPLess disorder (-∆S)More chemical energy in bonds (+∆H)∆G is negative - reactants have more free energy than products, energy is released and available to do work,Spontaneous (releases energy): exergonicCatabolic reactions have -∆G, release ATPMore disorder (+∆S)Less chemical energy in bonds (-∆H)Enthalpy (H) – total amount of energyEntropy (S) – degree of disorder∆G = ∆H - ∆STHydrolysis of ATP release energyATP + H2O ADP + PiExergonic reaction, releases energyADP contains less chemical potential energy in its bonds than ATPHydrolysis of ATP release chemical energy, allows ATP to drive chemical reactionsNon Spontaneous Reactions∆G for forward and reverse reactions have same absolute valueCoupling of non-spontaneous reaction to a spontaneous one drive non-spontaneous reaction, as long as net ∆G is negativeEnergetic coupling spontaneous reaction drives non-spontaneous one, provides thermodynamic driving force of a non-spontaneous biochemical reactionMost common reaction w/ energetic coupling hydrolysis of ATPADP is an energy acceptor and ATP is and energy provider∆G more negative than that of ATP hydrolysis give phosphate group to ADP∆G less negative than that of ATP hydrolysis receive phosphate group from ATP by energetic couplingEnzymesCatalysts: substances that increase rate of reaction, catalysts are usually proteins called enzymesEnzymes reduce activation energy of reactionTransition state: intermediate stage between reactants and products, highly unstable, has large amount of free energyTo reach transition state reactant must absorb energy from surroundingsAll reactions require input of energy (energy barrier)Activation energy energy input necessary to reach transition stateLower the energy barrier, faster reaction; higher barrier, slower reactionEnzymes reduce activation energy by stabilizing transition state and decreasing free energy; changes path of reaction between reactants and products, but not starting or end pointEnzymes form a complex with reactants and productsReactant = substrateSubstrate first forms complex with enzymeIn complex, substrate is converted to productComplex dissociates, releasing enzyme and productEnzyme folds into 3D shape, bring particular amino acids close to each other to form active siteActive site is portion of enzyme that binds substrate and converts it to productEnzymes reduce activation energy by positioning 2 substrates to react, aligning their reactive chemical groupsEnzyme activity can be influencedInhibitors: decrease activity of enzymesCommon, synthesized naturally by plants and animals, many drugs to treat infections/cancerIrreversible inhibitors: form covalent bonds with enzymes, irreversibly inactive themReversible inhibitors: form weak bonds with enzymes, easily dissociate from themCompetitive inhibitors: bind to active site of enzyme, prevent binding of substrate (compete with substrate for active site of enzyme), often structurally similar to substrate, reduce affinity of enzyme for substrate, can be overcome by increasing concentration of substrateNon-competitive inhibitors: have structure very different from substrate, bind to enzyme at different site from active site, no change in affinity of enzyme for its substrate, slows down reaction by altering shape of enzyme and reducing activityActivators: increase activity of enzymesAllosteric enzymes in cell regulated by activators and inhibitorsNegative feedback: final product inhibits first step of the reactionAllosteric enzyme: bind to activators and inhibitors at sites that are different from active site, result in change in shape and activity of enzymeCatalyze key reactions in metabolism, usually found at/near start of metabolic pathway or crossroads between 2 metabolic pathwaysCofactor: substance that associates with an enzyme and plays a key role in its functionMetallic cofactors: bind to diverse proteins, including those used in DNA synthesis, nitrogen metabolism, and transport of electrons for cellular respiration and photosynthesisMetal ions catalyze chemical reactions by themselvesCellular RespirationSeries of catabolic reactions convert energy stored in fuel molecules into chemical form that can be readily used in cellsAerobic respiration: occur in presence of oxygenOxygen consumed, CO2 and H2O producedStage 1: glucose, fatty acids, or amino acids are partially broken down and some energy is releaseGlucose breaks down to pyruvate glycolysisStage 2: Pyruvate converted to molecule acetyl-coenzyme A (acetyl CoA), CO2 is producedStage 3: citric acid cycle, acetyl-CoA broken down, more CO2 releasedStages 1-3: chemical energy transferred to ATP and electron carriersStage 4: oxidative phosphorylation, electron carriers donate their high
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