PowerPoint PresentationSlide 2An organism at equilibrium with the environment is no longer aliveEnergy conversion in biological systems is used to perform workCycling of resources and waste between environment and a living cell provides materials for energy conversionMetabolic redox reactionsRedox reactions are catalyzed by enzymes that permit the energy to be captured as workAerobic respiration uses redox reactions to interconvert chemical energy available from glucose oxidation into stored energy as ATPThermodynamic principles govern energy conversion in metabolic processesFirst Law of ThermodynamicsThe energy available for oxidation of a reduced compound in a biological system can be determined precisely using a device called a bomb calorimeter. A bomb calorimeter measures the change in temperature that occurs when a compound is completely oxidized. For example, the amount of stored energy in glucose.The definition of a CalorieTotal energy potential of 1 gram of glucose is the same regardless of the metabolic path taken, i.e., 15.7 kJ of energy. We can use this experimental value to calculate metabolic energy available from glucose oxidation. Note that the total amount of energy available does not tell you if glucose oxidation is favorable or not, for that, you need to know the change in Gibbs Free Energy (G).Second Law of ThermodynamicsThe physical state of H2O is an example of how entropy and energy are relatedGibbs Free Energy is a term relating enthalpy, temperature, and entropy in a way that predicts the spontaneity of a reactionThe equilibrium constant, Keq, is the ratio of the product and reactant concentrations when the reaction has reached equilibriumThe importance of G in metabolism is that it can be used to predict the direction of a reaction under physiological conditionsHow do G and Gº’ relate to metabolism?Coupled reactions share metabolic intermediates and combine endergonic and exergonic reactions to yield an overall G that is favorableOne type of shared reaction is one in which ATP hydrolysis (phosphoryl transfer) is used as a source of energy to drive unfavorable reactionsMetabolic flux is a term that explains the flow of metabolites through a set of link reactionsAn example of an ATP-coupled reaction in which both substrate concentration and enzyme activity combine to increase metabolic fluxSlide 24Slide 25Metabolic flux is affected by the availability of ATP which is needed as a substrate for numerous coupled reactions in the cellThe Energy Charge of the CellAdenylate forms are recycled in the cell by two major biochemical processes; the adenylate kinase reaction and phosphorylating systemsThe Energy Charge in the cell is maintained between 0.7 and 0.9 as are result of regulated flux through anabolic and catabolic pathwaysRelative metabolic flux through catabolic and anabolic pathways responds to changes in the Energy Charge in the cell to maintain homeostasisBioenergetics and Metabolism:Energy Input Restrains Entropy Metabolic Flux is Highly-Regulated Bioc 460 Spring 2008 - Lecture 24 (Miesfeld)Entropy wins every timeLife on earth requiresenergy from the sunThe flux of people through the DC metro is similar to the flux of metabolites in cells•Living organisms must have a constant input of energy in order to maintain a homeostatic condition that is far from equilibrium: an organism at equilibrium with the environment is no longer alive.•Sunlight is the ultimate source of energy for life on earth. Photosynthetic organisms convert sunlight energy into carbohydrates using redox reactions. Carbohydrates are a rich source of redox energy which is converted to phosphoryl transfer energy in the form of ATP.•The Energy Charge (EC) is a measure of [ATP], [ADP], and [AMP] in the cell and reflects the amount of available ATP for metabolic reactions. A low EC simulates flux through catabolic pathways that replenish ATP levels, whereas, a high EC stimulates flux through anabolic pathways to build up carbohydrate and lipid stores.Key Concepts in Bioenergetics and MetabolismAn organism at equilibrium with the environment is no longer alive Energy is required to keep the level of glucose higher inside the saguaro than outside in the desert. Similarly, energy is required to keep the level of NaCl lower inside the whale than in the sea water.What is the source of energy for the saguaro, what about the whale?Energy conversion in biological systems is used to perform work•Chemical work in the form of macromolecular biosynthesis of organic molecules.•Osmotic work to maintain a concentration of intracellular salts and organic molecules that is different than the extracellular milieu.•Mechanical work in the form of flagellar rotation or muscle contraction.Cycling of resources and waste between environment and a living cell provides materials for energy conversion Photosynthetic autotrophs use solar energy to oxidize water and generate chemical energy that us used to convert CO2 into carbohydrate (C6H12O2).Heterotrophs are dependent on photosynthetic autotrophs, or other heterotrophs, to provide the chemical energy needed for life. The byproducts of aerobic respiration are CO2 and water.Metabolic redox reactions•Both photosynthesis and aerobic respiration interconvert energy using a series of linked oxidation and reduction reactions, also called redox reactions, to transfer electrons (e-) between metabolites.• Oxidation Is Loss of electrons and Reduction Is Gain of electrons (OIL RIG).•Since electrons cannot exist free in solution, they must be transferred between compounds, this transfer process is controlled by enzymes in biological systems.Redox reactions are catalyzed by enzymes that permit the energy to be captured as workAerobic respiration uses redox reactions to interconvert chemical energy available from glucose oxidation into stored energy as ATP Nicotinamide adenine dinucleotide (NAD), flavin adenine dinucleotide (FAD), and quinone (Q) are electron carriers in numerous biochemical reactions.Thermodynamic principles govern energy conversion in metabolic processes• First Law of Thermodynamics:The total amount of energy in the universe does not change; energy can neither be created or destroyed. Energy conversion in biological systems is never 100%.• Second Law of Thermodynamics:In the absence of energy input, all natural processes in the universe tend toward disorder, the measure of this disorder, or randomness, is called
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