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Energy and Metabolism Adapted from:

Jan 21, 2016



  • Energy and MetabolismAdapted from:

  • MetabolismThe sum of all the chemical reactions occurring in an organism at one timeConcerned with the management of material and energy resources within the cellAnabolic pathwaysCatabolic Pathways*

  • *BioenergeticsStudy of how organisms manage their energy resourcesEnergy: the capacity to do work, to move matter-kinetic energy: the energy of motion-potential energy: stored energyEnergy can take many forms:mechanicalelectric currentheatlight

  • *Flow of EnergyPotential energy stored in chemical bonds can be transferred from one molecule to another by way of electrons.**the rearrangement of atoms in molecules may results in the potential energy of the molecule being converted into kinetic energy.

    oxidation: loss of electronsreduction: gain of electronsredox reactions are coupled to each other.

  • *Laws of Thermodynamics The terms of open or closed systems refer to whether or not energy can be transferred between the system and its surroundings (can energy be imported or exported)

    First Law of Thermodynamics energy cannot be created or destroyed-energy can only be converted from one form to anotherFor example:sunlight energy chemical energy photosynthesis

  • *Laws of ThermodynamicsA change in free energy can occur with metabolism:endergonic reaction: a reaction requiring an input (gain) of energy (products contain more energy)exergonic reaction: a reaction that releases (lose) free energy (reactants contain more energy)Metabolic reactions are often coupled where an exergonic reaction fuels an endergonic reaction.

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  • *Laws of ThermodynamicsMost reactions require some energy to get started. Can you think of two examples?activation energy: extra energy needed to get a reaction started-destabilizes existing chemical bonds-required even for exergonic reactionscatalysts: substances that lower the activation energy of a reaction

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  • ObjectivesExplain the role of ATP in the cellDescribe ATPs composition and how it performs cellular workExplain the importance of chemical disequilibriumUnderstand the energy profile of a reaction including: activation energy, free energy change & transition state.Explain how metabolic pathways are regulated.*

  • *Energy is required to form bonds.Atoms or molecules

  • *Energy is released when bonds are broken.The energy is now released. It may be in a form such as heat or light or it may be transferred to another molecule.Menu

  • *Energy Currency of CellsATP = adenosine triphosphate-the energy currency of cells

    ATP structure:-ribose, a 5-carbon sugar-adenine-three phosphates

  • *ATP (Adenosine Triphosphate)

  • *ATP (Simplified Drawing)ABase (adenine)Sugar (ribose)3 phosphate groups

  • *AATPATP Stores Energy

  • *Energy Currency of Cells

    Phosphates are highly negative, therefore:-the phosphates repel each other-much energy is required to keep the phosphates bound to each other-much energy is released when the bond between two phosphates is brokenATP has a high DG

  • *Energy Currency of CellsWhen the bond between phosphates is broken:ATP ADP + Pi energy is released (DG=-7.3Kcal/mol in the lab, -13 Kcal/mol in the cell)ADP = adenosine diphosphatePi = inorganic phosphate

    Is this reaction catabolic or anabolic? This reaction is reversible.

  • *Coupled Reactions

    ATP is RecycledThe energy used to produce ATP comes from glucose or other high-energy compounds.ATP is continuously produced and consumed as illustrated below.

  • Phosphorylation*ATP is synthesized from ADP + Pi. The process of synthesizing ATP is called phosphorylation.Two kinds of phosphorylation Substrate-Level PhosphorylationChemiosmotic Phosphorylation

  • Electron CarriersCompounds that pick up electrons from high energy compounds and transfer then to low-energy compounds.LEO & GERElectrons carry reducing powerEg. NAD+ and FAD (oxidized forms), NADH and FADH2 (reduced forms)Coupled reaction


  • *EnzymesMultienzyme complexes offer certain advantages:1. The product of one reaction can be directly delivered to the next enzyme.2. The possibility of unwanted side reactions is eliminated.3. All of the reactions can be controlled as a unit.

  • *MetabolismBiochemical pathways are a series of reactions in which the product of one reaction becomes the substrate for the next reaction.

    Biochemical pathways are often regulated by feedback inhibition in which the end product of the pathway is an allosteric inhibitor of an earlier enzyme in the pathway.

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    8811G = free energy, the energy available to do work*13The energy released when ATP is broken down to ADP can be used to fuel endergonic reactions.

    The energy released from an exergonic reaction can be used to fuel the production of ATP from ADP + Pi.