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Chapter 9 新陈代谢和生物能学

Chapter 9 新陈代谢和生物能学. The total energy of the universe is constant; the total entropy is continually increasing. — Rudolf Clausius, 1867. 2010.10.29. 生命的最基本特征 : 新陈代谢. 代谢途径 : 分解代谢 (catabolism) 合成代谢 (anabolism) 代谢种类：物质代谢 能量代谢. 合成代谢是需能过程，一般由磷酸基团的转移形成 ATP 来贮存能量；

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Chapter 9 新陈代谢和生物能学

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  1. Chapter 9 新陈代谢和生物能学 The total energy of the universe is constant; the total entropy is continually increasing. — Rudolf Clausius, 1867 2010.10.29

  2. 生命的最基本特征: 新陈代谢 代谢途径:分解代谢(catabolism) 合成代谢(anabolism) 代谢种类：物质代谢 能量代谢

  3. 合成代谢是需能过程，一般由磷酸基团的转移形成ATP来贮存能量；合成代谢是需能过程，一般由磷酸基团的转移形成ATP来贮存能量； GTP, UTP, CTP. NADH, NADPH和FADH CoA(-acetyl) 分解代谢是产能过程

  4. 糖 2H TAC 氧化磷酸化 乙酰CoA 脂肪 蛋白质 CO2 ATP 三大营养素可在体内氧化供能。 共同中间产物 共同最终代谢通路 三大营养素

  5. 从能量供应的角度看，三大营养素可以互相代替，并互相制约。从能量供应的角度看，三大营养素可以互相代替，并互相制约。 一般情况下，机体优先利用燃料的次序是糖原、脂肪和蛋白质。供能以糖及脂为主，并尽量节约蛋白质的消耗。

  6. 新陈代谢的化学反应机制 • 基团转移：如酰基、磷酸基团的转移 • 氧化还原：如与电子传递链偶链的氧化反应 • 消除、异构化和重排：如糖酵解中的磷酸烯醇式丙酮酸的异构 • 碳- 碳键的形成或断裂

  7. 体系： • 封闭体系 • 隔离体系 • 开放体系 状态函数：体系所处的状态，由其热力学性质（压力、体积、温度、表明张力等）等决定，这种状态和性质之间的对应关系称为热力学状态函数 内能 (E): 体系内部质点能量的状态函数 焓 (H): 体系内部所有质点热能的状态函数 ∆H = ∆E + ∆PV

  8. 热力学第一定律：能量守恒定律，即一个体系和其周围环境的总能量是一个常数热力学第一定律：能量守恒定律，即一个体系和其周围环境的总能量是一个常数 W近似为零（生化体系接近恒温恒压） ∆E = Q - W Q = ∆E = ∆H

  9. 热力学第二定律：热的传导只能由高温物体传至低温物体；即热的自发逆反应是不可能的热力学第二定律：热的传导只能由高温物体传至低温物体；即热的自发逆反应是不可能的 熵(S): 体系能量分散程度（无序热运动）的状态函数 ∆S总= ∆S体系+ ∆S环境〉0 所有自发进行的过程都是不可逆的过程，熵值总是增加的，直到达到最大值才停止 为什么生物有机体能保持有序结构？ 生物有机体能不断形成有序结构是因为它产生的负墒完全由周末环境的熵增抵消，并且在总和上是正值

  10. 负墒也是信息的依托 世事的起伏本来是波浪式的，人们要是能够趁着高潮一往直前，一定可以功成名就；如果不能把握时机，就要终身蹭蹬，一事无成。

  11. 自由能 (G): 热力学过程中，系统减少的内能中可以转化为对外作功的部分 ∆G = ∆E - T∆S units of ∆G and ∆H are J/mole or Cal/mole (1 Cal =4.184 J); units of S are J/moleKelvin (J/molK) ∆G=0; reversible ∆G<0; ? ∆G>0; ?

  12. units of ∆G and ∆H are J/mole or Cal/mole (1 Cal =4.184 J); units of S are J/moleKelvin (J/molK) Constant temperature and pressure (most physiological conditions) ∆G=0; reversible ∆G<0; ? ∆G>0; ?

  13. 标准自由能变化与平衡常数的关系 Under standard conditions (298 K= 25°C), when reactants and products are initially present at 1 M concentrations or, for gases, at partial pressures of 101.3 kilopascals (kPa), or 1 atm, the force driving the system toward equilibrium is defined as the standard free-energy change, Go the standard state for reactions that involve hydrogen ions is [H+] 1 M, or pH 0. Most biochemical reactions, however, occur in well-buffered aqueous solutions near pH 7; both the pH and the concentration of water (55.5 M) are essentially constant. For convenience of calculations, biochemists therefore define a different standard state, in which the concentration of H+ is 10-7 M (pH 7) and that of water is 55.5 M; for reactions that involve Mg2+ (including most in which ATP is a reactant), its concentration in solution is commonly taken to be constant at 1 mM. G’o

  14. Go = ∑Go产物 - ∑Go反应物 = Q G= Go+ RT ln Q G= 0, reaction reaches equilibrium: Go' = -RT ln K'eq

  15. Go' = -2.303RT lg K'eq • The actual free energy change (G’ ) determines whether a reaction occurs spontaneously • The standard free energy change in biochemistry (Go') is a constant. • G’ for a reaction can be larger, smaller, or the same as Go'depending on the concentrations of the reactants and products.

  16. Chemical analysis shows that whether we start with any concentration, the final equilibrium mixture at 25º C and pH 7.0 will be the same: 1 mM glucose 1-phosphate and 19 mM glucose 6-phosphate. Because the standard free-energy change is negative, when the reaction starts with 1.0 M glucose 1-phosphate and 1.0 M glucose 6-phosphate (In[glucose 1-phosphate]/[glucose 6-phosphate]=0), the conversion of glucose 1-phosphate to glucose 6-phosphate proceeds with a loss (release) of free energy.

  17. The G and Go’values are additive (可加和的) when reactions are coupled, thus a thermodynamically unfavorable reaction can be driven by a favorable one. • The overall K`eq is multiplicative (the product of two,两值相乘), although Go'is additive (the algebraic sum of two，两值相加).

  18. (under standard conditions, the reaction will tend not to proceed spontaneously) In thermodynamic calculations, all that matters is the state of the system at the beginning of the process and its state at the end; the route between the initial and final states is immaterial.

  19. ATP is the universal currency for biological energy • This was first perceived by Fritz Lipmann and Herman Kalckar in 1941 when studying glycolysis. • Hydrolysis of the two phosphoanhydride (磷酸酐键) bonds in ATP generate more stable products releasing large amount of free energy • The ATP molecule is kinetically stable at pH 7 and enzyme catalysis is needed for its hydrolysis. • ATP actually exists as a sum of various species in cells (e.g., ATP4- and Mg2+ATP2-).

  20. Fig. 2. The two-dimensional stick model of the adenosine phosphate family of molecules, showing the atom and bond arrangement. g b a

  21. ATP Provides Energy by Group Transfers, Not by Simple Hydrolysis

  22. Other Phosphorylated Compounds and Thioesters Also Have Large Free Energies of Hydrolysis

  23. ATP is not a long-term storage form of free energy in living cells, but phosphocreatine (磷酸肌酸) is one such phosphoryl reservoir, or so-called phosphagen (磷酸原).

  24. Transphosphorylations between Nucleotides GTP, UTP, and CTP dATP, dGTP, dTTP, dCTP

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