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Princípios Físicos Aplicados à Fisiologia (PGF5306-1) 14 Prof. Adriano Mesquita Alencar Dep. Física Geral Instituto de Física da USP ENERGY TRANSFORMATION B02 Energia Aula 11 sábado, 5 de outubro de 13 Princípios Físicos Aplicados à Fisiologia (PGF5306-1) sábado, 5 de outubro de 13 Entalpia, H H= ON U + RT n R, é uma constante universal, 8.3145 J/K mol Em um experimento dessa bomba de calorímetro com Etanol, a 298K e volume constante, 1368 kJ/mol de calor é liberado Fig. 1.11 Schematic diagram of a bomb calorimeter. A sample is placed in the reaction chamber. The chamber is then filled with oxygen at high pressure (>20 atm) to ensure 2 complete. 5 Electrical heating of a wire 2 initiates the reaction. that the reaction is fast and The increase in water temperature resulting from the combustion reaction is recorded, and the temperature change is converted into an energy increase. The energy change is sábado, 5 de outubro de 13 C H OH(`) + 3O (g) ! 2CO2 (g) + 3H2 O(`) !1 !1 Entalpia, H H= U + RT n H= U + 298 · 8.3145 n H= U + 2478 n C2 H5 OH(`) + 3O2 (g) ! 2CO2 (g) + 3H2 O(`) n=2 H= 3=1 1368000 2478 (J/mol) Se a variação de entalpia é negativo o processo é exotérmico. Caso contrario o processo é endotérmico sábado, 5 de outubro de 13 Entalpia, H C2 H5 OH(`) + 3O2 (g) ! 2CO2 (g) + 3H2 O(`) H H H C C H H H O +3( O O H ) H + 2 (O C Liquido para Gas = 277 O) +3( O H Liquido para Gas = 41 ((5*415+346+358+464)+277)+3*498 (2*2*805+6*464+(3*41)) ΔHο= -1113 (saindo do estado liquido) 1 ο ΔH = -1267 (estado gasoso para todos) C ΔHο= -1368 kJ/mol (Valor de Tabela) sábado, 5 de outubro de 13 C ! 346 C = C ! 602 C H H ! 415 H ! 436 O = O ! 498 C = O ! 1077 em Monoxido C = O ! 805 em Dioxido C O ! 358 O H H ! 464 Cl ! 432 ) C2 H5 OH(`) + 3O2 (g) ! 2CO2 (g) + 3H2 O(`) H H H C C H H H +3( O O H ) O H + 2 (O C O) +3( O H ) 6H + 2C + 7O átomos Entalpia H H H C C H H H +3( O O H H H C C H H O H O H C C H H gás liquido H C O H H C C H H +3( O O O O +277 +3( O H ) H H ) + 2 (O 1 H +3( + 2 (O O O ) 1 C O) +3( -123 H O) C +3( O gás H H ) O) -6004 H 1 sábado, 5 de outubro de 13 + 2 (O +4737 H +3( O H H ) gás gás H 1 O H H ) H ) gás ) H + 2 (O C gás O) +3( O liquido Bioquímica • Aproximadamente 1/2 da massa seca do corpo humano é de proteinas • O estado nativo das proteínas é “folded”, empacotado - uma espécie de cristal orgânico • Mesmo nesse estado existe flutuação na estrutura do caroço central. • Estado empacotado - parecido com solido • Estado desempacotado - parecido com liquido sábado, 5 de outubro de 13 Table 2.2. Energetics of non-covalent interactions between molecules 1 kcal Type of interaction Equation Ion–ion Ion–dipole Dipole–dipole Ion–induced dipole Dispersion E ¼ q1q2/Dr E ¼ q„!/Dr2 E ¼ „1„2!0 /Dr3 2 2 4 E ¼ q fi/2Dr r E ¼ 3h”fi2/4r6 a = 4.18 kJ Approximate magnitude !1 (kcal mol ) 14 !2 to þ2 !0.5 to þ0.5 0.06 0 to 10 Charge q1 interacts with charge q2 at a distance r in medium of dielectric D. b Charge q interacts with dipole „ at a distance r from the dipole in medium of dielectric D. ! and !0 are functions of the orientation of the dipoles. c Dipole „1 interacts with dipole „2 at an angle q relative to the axis of dipole „2 and a distance r from the dipole in medium of dielectric D. d Charge q interacts with molecule of polarizability at fi distance r from the dipole in medium of dielectric D. e Charge fluctuations of frequency ” occur in mutually polarizable molecules of polarizability fi separated by a distance r. The data are from Table 1.1 of van Holde (1985). sábado, 5 de outubro de 13 Charge q interacts with molecule of polarizability at fi distance r from the dipole in medium of dielectric D. e Charge fluctuations of frequency ” occur in mutually polarizable molecules of polarizability fi separated by a distance r. The data are from Table 1.1 of van Holde (1985). Bioquímica Table 2.3. Characteristics of hydrogen bonds of biological importance Bond type Mean bond distance (nm) O–H . . . O O–H . . . O! ... O–H N Nþ–H . . . O N–H . . . O N–H . . . N ... HS–H SH2 0.270 0.263 0.288 0.293 0.304 0.310 — !1 Bond energy (kJ mol ) !22 !15 !15 to !20 !25 to !30 !15 to !25 !17 !7 The data are from Watson (1965). ideal case all amino acid side chains are completely exposed to solvent (Table 2.4). The non-covalent interactions that stabilize folded protein strucsábado, 5 de outubro de 13 Table 2.4. Principal features of protein structure Folded (native) state Highly ordered polypeptide chain Intact elements of secondary structure, held together by hydrogen bonds Intact tertiary structure contacts, as in an organic crystal, held together by van der Waals interactions Limited rotation of bonds in the protein core Desolvated side chains in protein core Compact volume Unfolded (denatured) state Highly disordered chain – “random coil” No secondary structure No tertiary structure Free rotation of bonds throughout polypeptide chain Solvated side chains Greatly expanded volume results from the concurrent breaking of a large number of weak sábado, 5 de outubro de 13 SOME EXAMPLES FROM BIOCHEMISTRY temperature at which a protein unfolds (or double-stranded elts) is called the melting temperature, Tm. This temperature s not only on the number and type of non-covalent bonds in ed state but also on the pH and other solution conditions. Tm pends on the pressure, but most biological science experire done at 1 atm pressure. In the case of proteins, changing 5 de outubrochanges de 13 ofsábado, solution the net charge on the protein surface. Fig. 2.7 Enthalpy of unfolding of hen egg white lysozyme as a function of transition temperature. Filled symbols: intact lysozyme. Open symbols: lysozyme in which one of the four native disulfide bonds has been removed. When folded, 3-SS lysozyme closely resembles the native state of intact lysozyme. Change in transition temperature was induced by a change of pH. Note that 1H is approximately linear in Tm. The data are from Cooper et al. (1991). 45 Fig. 2.8 Isothermal titration calorimeter. The temperature is constant. There are two identical chambers, the sample cell and the Isothermal titration reference cell. In most cases, the ter. The temperature is sample cell will contain a . Theremacromolecule, are two identical and the syringe/ stirrer is used inject a ligand into s, the sample cell toand the sample cases, cell. Thethe syringe is e cell. the In most usually coupled to an injector cell willsystem contain a under software control and olecule,rotated and the syringe/speed. The at a constant reference is filledinto with buffer; used to inject cell a ligand no reaction occurs there. 1T ple cell.measures The syringe is the temperature oupleddifference to an injector between cells, which are surroundedcontrol by insulation under software andto minimize heat exchange with the at a constant speed. The surroundings. Electronic (power e cell isfeedback) filled with buffer; circuitry minimizes 1T on a continuous basis. If injection of ion occurs there. 1T ligand results in binding, there will s the temperature ordinarily be a change in the e between cells, ofwhich are The temperature the sample. of the change ded by sign insulation to will depend on whether the reaction is exothermic e heat exchange with the or endothermic. An experiment dings. Electronic (power injections consists of equal-volume from the syringe into the sample k) circuitry minimizes 1T tinuouscell. basis. If injection of sults in binding, there will y be a change in the sábado, outubro de 13 The ture of5 de the sample. What if we’re interested in the energetics of an enzyme binding to its substrate? This can be measured if a suitable substrate analog can be found or the enzyme can be modified. For instance, ITC has been used to measure the enthalpy of binding of a small compound called 20 -cytidine monophoshate (20 CMP) to ribonuclease A, which hydrolyzes RNA to its component nucleotides. 20 CMP binds to and inhibits the enzyme. If the enzyme of interest is, say, a protein phosphatase with a nucleophilic cysteine in the active site, mutation of the Cys to Ser or Asn will abolish catalytic activity, as in the What if we’re interested in the energetics of an enzyme bind N-terminal domain of the cytoskeleton-associated protein tensin, to itsand substrate? Thisofcan be measured if a suitable substrate ana the energetics binding can be studied. A deeper underof binding be sought in be Chapters 5 and 7.For instance, ITC can standing be found or thewill enzyme can modified. Fig. 2.10 Differential scanning calorimetry. (A) Schematic diagram of the instrument. In this case the reference cell contains buffer only, and the sample cell contains the macromolecule dissolved in buffer. Both cells are !1 heated very slowly (e.g. 1 " C min ) in order to maintain equilibrium, and feedback electronic circuitry is used to add heat so that 1T # 0 throughout the experiment. Other types of DSC have been used for other purposes in biophysics, for example, to investigate the physiological limits of the freeze tolerance and freeze-avoidance strategies taken by different insect species to survive subzero temperatures. (B) Data. The heat added to keep 1T # 0 can be plotted as a function of temperature. The endothermic peak corresponds to heat absorbed, for example, on protein denaturation. The peak maximum corresponds roughly to the transition temperature, or melting temperature. The area below the peak is 1Hd(Tm). The heat capacity of the unfolded state of a protein minus the heat capacity of the folded state is 1Cp,d. There is more about DSC in Chapter 5. sábado, 5 de outubro de 13 Hidratação e desidratação iônica ocorre constantemente nos canais/bombas de íons e na transmissão de impulsos nervosos. Table 2.5. Standard ion hydration enthalpies Hþ þ Li Naþ þ K — NH4þ #1090 #520 #405 #321 — #301 Mg2þ 2þ Ca Ba2þ 2þ Fe 2þ Zn Fe3þ #1920 #1650 #1360 #1950 #2050 #4430 The data refer to Xþ(g) ! Xþ(aq) at 1 bar and are from Table 2.6c in Atkins (1998). 1 bar ¼ 10 5 Pa ¼ 105 N m#2 ¼ 0.987 atm. 1 Pa ¼ 1 pascal. Blaise Pascal (1623–1662) was a French scientist and religious philosopher. H. Heat capacity sábado, 5 de outubro de 13 Energias Energias mais relevantes para sistemas biológicos: 1. Energia Química 2. Energia Mecânica 3. Energia Eletromagnética 4. Energia Térmica sábado, 5 de outubro de 13 Fotossíntese Energias Energias mais relevantes para sistemas biológicos: 1. Energia Química 2. Energia Mecânica 3. Energia Eletromagnética 4. Energia Térmica Deterministicas Movimento Browniano Térmicas A razão entre a escalas derteminísticas e termicas é: Forcas no interior da célula sábado, 5 de outubro de 13 Edet /kB T A razão entre a escalas derteminísticas e termicas é: Edet /kB T kB T = 4.1 pN nm = 0.6 kcal/mol = 2.5 kJ/mol = 25 meV 1010 Electrostatic energy of a spherical shell 105 Bending of a 20:1 rod ENERGY ( joules) 100 10 Fracture of a 20:1 rod 5 10 10 10 15 10 20 10 25 10 30 Proton Nucleus Chemical bonds Thermal energy Binding energy of an electron in a box 10 15 10 12 10 9 10 6 10 3 100 LENGTH (meters) Maquinaria molecular: de Hidrogênio (quadrado), grupos fosfato emmechanical, ATP (triângulo), Figure 2. The confluence Ligação of energy scales is illustrated in this graph, which shows how de thermal, chemical, and electrostatic energies associated with an object scale with size. As the characteristic object de size approaches that at which energia moligações covalentes (círculo), energia de torção (azul), energia fratura (verde), lecular machines operate (shaded), all the energies converge. The horizontal line shows the thermal energy scale kT which, of eletrostática and R. Quake, Physics Today (2006)] course, does(laranja). not depend[Rob on an Phillips object’s size. We Stephen estimate binding energy (purple) by considering an electron in a box; for com- parison, the graph shows measured binding energies for hydrogen bonds (square), phosphate groups in ATP (triangle), and cosábado, 5 de outubro de 13 (circle), along with characteristic energies for nuclear and subatomic particles. In estimating the bending energy valent bonds OH H OH H A A A A Geração de Energias (Glicolise) P P P P P P P P 2 2 2 A P P P A N P P P P 2 N A 4 Carbohydrate Metabolism A 151 A. Glycolysis: balance O O O 8 P O C HC H P HC H 2 O O C CH2 HO 2 P P 2 2 A P 1 6 lucose 6-phosphate omerase 5.3.1.9 -Phosphofructonase 2.7.1.11 ructose bisphosphate dolase 4.1.2.13 riose-phosphate omerase 5.3.1.1 -20 Glyceraldehyde3- P dehydrogenase 1.2.1.12 7 Phosphoglycerate O 2.7.2.3 O kinase 8 Phosphoglycerate 8 HC5.4.2.1 O P mutase C H2C OH Phosphopyruvate hydratase 4.2.1.11 2 2-Phosphoglycerate Pyruvate kinase 10 2.7.1.40 9 sábado, 5 de outubro de 13 2 H 2O A H2C P O CH2 O A OH C P Glyceraldehyde2 3-phosphate COO COO C C O CH3 O CH3 Glycerone P P P 3-phosphate Pyruvate Pyruvate O CH2 H1 OH H H OH 2 P P A P P P P P P 2 A HC H2C O P P O glycerate A 2 P P P ∆G' (kJ · mol-1) N A 7 3-Phospho2-80 A P 4 OH N P P A P P P P P P P 3 -60C P P P A P A A A CH2 OH O H HO CH2 O H O 2 A A 2 O P Pyruvate possui H HO 2 3 grande valor CH OH H OH H OH H energético e pode ser utilizado para 2 2 4 produzir mais ATP. Assim, uma 5 8 9 O H O O molécula de glicose C C H C OH 5 pode 6 HC OH HC 6OH 7 C O gerar até 30 10 C O H HC O O CH ATPs. 2 Glycerone 1,3-BisphosphoGlyceraldehyde P P P P P -40 Steps 1, 3 and 10 2 OHin are CH bypassed O gluconeogenesis O P A O OH HO Fructose 1,6-bisphosphate Fructose 6-phosphate A A 9 H C O P ∆GOI = 2–35 kJ · mol–1 P P P H P P P exokinase 2.7.1.1 N 5 Glycolysis 2 H H H OH Pyruvate P P P 2 OH 0 Glucose 6-phosphate Glucose HO A C C. Energy profile CH3 spholpyruvate 2 H HC P glycerate Glucose OH H H2 O A 6 O CH HO O OH 10 P N H OH 1,3-Bisphospho2 A B. Reactions O P 2 OH H2C HO glycerate 2 H 2O O OH H 2 3-Phospho- hosphocerate O OH H7 O O C CH2 HO OH H2C OH O 2 P A 2 P P 2 P P P P 2 glycerate 3-phosphate Pyruvate C. Energy profile 3-phosphate Koolman, Color Atlas of Biochemistry, 2nd edition © 2005 Thieme Geração de Energias sábado, 5 de outubro de 13 Armazenamento de Energias kB T = 4.1 pN nm = 0.6 kcal/mol = 2.5 kJ/mol ATP = 25 meV C C ! 346 kJ/mol C = C ! 602 C H H ! 415 H ! 436 O = O ! 498 Pi AT P + H2 O ! ADP + Pi sábado, 5 de outubro de 13 ADP 30.5 > Go > 50 kJ/mol A. ATP: structure Phosphoric acid ester bond N O O O Pβ O Pα O O O O CH2 O H H H H O O OH OH Pβ O Pα O O O 1. Formula Mg 2. Mg2 C N Pγ O O C HC O CH2 O H H C N bond N CH γ β Ribose α Phosphate residue OH -Complex N-glycosidic NH2 Adenine Phosphoric acid anhydride bonds Adenosine B. Hydrolysis energies P P P + P P 1. Hydrolysis energies C. Types of ATP formation + Adenosine AMP + -30 sábado, 5 de outubro de 13 4 P ATP -20 + ADP -10 3 P ATP ∆G OI kJ · mol-1 2 ATP 1 P P P 1 2 3 Positive Neutral Negative 2. ATP: charge density Koolman, Color Atlas of Biochemistry, 2nd edition © 2005 Electrons ATP-ADP ~ varias tipos de reações bioquímicas ATP-ADP ~ 20 kBT Ligação covalente típica ~ 150 kBT NADP+ sábado, 5 de outubro de 13