Enzymes speed up metabolic reactions by lowering energy barriersEnzyme: macromolecule that acts as a catalyst- chemical agent that speeds up reactions without being consumed by the reaction.Activation EnergyChanging one molecule into another involves changing the starting molecule into a unstable state. When bonds of the product molecules form, molecules return to stable shapes with lower energy than contorted shape.Activation Energy (E)- initial energy for starting a reaction. Energy required to contort the reactant molecule so bonds can break.Often supplied as thermal energy. Reactant absorbs energy from surroundings.Transition state- Molecules have formed enough energy for bonds to breakAt summit, when Energy=Ea reactants are in transition stateG<0 is exergonic and occurs spontaneously.Reacts must absorb enough energy to rach the top of the activation energy barrier before reaction can occur.Enzymes lower the Ea BarrierEnzymes catalyze reaction by lowering Ea and enabling reactant to absorb energy to reach transition state even at moderate temperatures.Enzymes does change G, only hasten reactions that would eventually occur anyways.Active site provides a template for 2 or more reactions to come together in proper orientationEnzyme stretches substrate molecules toward transition-state form already breaking some of the bonds for the reaction.Active site may provide a microenvironment that is better for that type of reaction (better pH)Active site may have a role in the chemical reaction. Brief covalent bonding with the substrate and amino acid of the enzyme.Saturated Enzymes- All of the enzymes have substrates in their active sites and the rate of the reaction is the fastest.Substrate Specificity of EnzymesSubstrate- enzyme acts onSubstrate EnThermodynamics- Energy for lifeMetabolism- sum of all chemical reactions occurring in a cell.Bioenergetics- study of energy flow across systemsCells are mini factoriesSynthesize large molecules from smaller subunitsBreak down large molecules into smaller subunitsTransport moleculesOrganize and Reorganize CytoskeletonEnergy needs to always be availableMetabolism: collection of biochemical reactions that occur in a cell – fundamental property of living tissueReactions are grouped in pathways product of one reaction is the substrate for anotherDivision of the Pathways-CatabolismCatabolism: Breakdown of larger, more complex molecules into smaller, less complex moleculesGenerates building blocks to assemble the complex molecular structures necessary for lifeTurns over unneeded moleculesReleases chemical energy needed to run other cellular processesAnabolism: synthesis of larger, more complex molecules from smaller, less complex moleculesRequires input of energyEverything aided by enzymesBioenergetics- study of energy flow through living systems. It is at every level of organizationEnergy- Capacity to do work Cells transform energy from 1 type to another.Potential – stored energy (chemical energy stored in molecules due to arrangement of atoms)Kinetic- energy of motion (thermal energy)Thermodynamics- Study of energy transformation in a collection of matterScientists study energy flow through a systemSystem is whatever is being studiedAnything not in the system is surroundings (rest of universe)Types of Systems1. Closed or Isolated System – No exchange between system and surroundings.2. Open System- Exchange of energy between system and surroundings. Organisms are open systems – constantly acquire energy and release metabolic wastes1st law of Thermodynamics- Total amount of energy is universe is constant. Energy cannot be created nor destroyed. Principle of the Conservation of Energy2nd law of Thermodynamics- There is a loss of usable energy when it is changed from one form to another HEAT.Entropy- measure of disorder or randomness of the universe. Energy transformations raise entropy.Living organisms are always fighting a two front, unwinnable warEntropy vs. EquilibriumEntropy always wins—it’s unstoppableSpontaneous Processes- Must increase entropy. These processes occur without input of energy.Nonspontaneous Processes- Don’t occur spontaneously. Going against natural flow of entropyGibbs Free Energy- Gibbs identified free energy. Measures energy a system has that is available to do work.Change in free energy as a reaction proceeds- tells if its spontaneousEnergy EquationH- Total energy in system (enthalpy)G- Free energy in a systemT Δ S- Amount of energy lost and unavailable to do workWe care about these changing- ΔΔH = ΔG + T ΔSChange in total amount of energy – change in usable energy + change in unusable energyΔG = ΔH - T ΔS tells us ΔG!Value of ΔG tells us about the progress of a reactionLarge ΔG is more free energy, less stable, greater work capacitySmaller ΔG is less free energy, more table, less work capacityDirectional Nature of Metabolism1. Most reaction are reversible: concentration drives them.More reactions to rightTo left More Products2. Chemical equilibrium = forward and reverse reactions proceed at equal rates without net change in concentration. Specific ratio3. Metabolic reactions rearrange atoms but never destroy them – 1st law.Metabolic1. Endergonic: Energy input/ lowers temperatureNOT spontaneousA+B + Energy Product+ ΔG products have more free energy than reactantsex) photosynthesis, dehydration synthesis2. Endergonic: Energy output/ heat lost/ spontaneousC A + B + Energy-ΔG products have less free energy than reactantsex) HydrolysisEquilibrium and MetabolismLeft alone, all reactions eventually reach equilibriumReactants and products at equilibrium have minimum free energyIf all reactions are at equilibrium, then there is no free energy available to do workNo work = Dead CellCellular WorkChemical Work: Anabolic reactions – building large moleculesMechanical Work: Any movement – Ciliary beating, muscle contraction, chromosome separationTransport work: Building gradients – pumping substances across a membrane against a gradientBioluminescence- chemical reaction emits lightATP drives processesATP + H2O(hydrolysis) ADP + inorganic phosphate + Energy1. Pentose sugar2. Adenine Nitrogen Base3. Phosphate GroupsWhy ATP specifically? Allows energy to be stored in the right form and right sizeWe don’t waste energy with ATPLose some energy in process of converting ATP but we get the best deal for the most partCoupled ReactionsEnergy gained in exergonic
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