Bioenergetics

• Metabolism is the highly coordinated cellular activity in which many multi-enzyme systems (metabolic pathways) cooperate to obtain chemical energy, convert nutrient molecules into the cell's own characteristic molecules, and polymerize monomeric precursors into biomolecules.
• For oxidation of FADH2, only 6 protons are pumped.
• Δ G is put to work for pumping H+ across the inner mitochondrial membrane.
• An electrochemical gradient is created.
• Upon creation of a proton gradient, protons flow back to the matrix to equalize charge distribution and by doing so, drives synthesis of ATP by ATP synthase.
• The gradient is relieved by passage of H+ through Complex V (ATP synthase).
• FADH2 enters Complex II which does not pump protons, thus, electrons from FADH2 pass through Complexes III and IV only.
• As the [H+] increases in the intermembrane space, it lowers the pH.
• Inhibitors of ATPase prevent influx of protons through ATP synthase.
• Entry of about 4 H+ allows synthesis of 1 ATP.
• Electron transport and ATP synthesis are coupled by a proton gradient (pH gradient and membrane potential) across the inner mitochondrial membrane.
• Inhibitors of ETC include AMYTAL, a barbiturate sedative, PIERICIDINE, an antibiotic, ANTIMYCIN A, an antibiotic, and CN-, CO, N3-, which inhibits electron flow in complex IV.
• ATP Synthase is an enzyme complex containing the catalytic site for the synthesis of ATP.
• Upon exposure of actively respiring mitochondria to these agents, ETC ceases to operate, clearly illustrating that ETC and ATP synthesis are indeed tightly coupled.
• The process of ATP synthesis is coupled at ATP synthesis from ADP + Pi.
• Upon oxidation of NADH, 10 protons are pumped.
• If 4 protons are needed to synthesize one mole of ATP, then for each NADH: ▪ 10/4 = 2.5 ATPs are produced, and for each FADH2: ▪ 6/4 = 1.5 ATPs are produced.
• Electrons are ultimately accepted by O2 in Complex IV to generate H2O ATP Synthase: Oxidative Phosphorylation Chemiosmotic Hypothesis: By Peter Mitchell in 1961
• Co-enzymes are not enzymes, but they act as activated carriers in metabolic reactions.
• Nernst Equation is used for different concentration.
• Metabolic reactions can be categorized as redox reactions, where reducing agents are substances that tend to give up electrons and be oxidized, and oxidizing agents are substances that tend to accept electrons and be reduced.
• Entropy (Δ S) is a measure of change in randomness or disorder of reactants and products, according to the second law of thermodynamics.
• Mathematical combination of the two gives rise to another thermodynamic quantity – free energy (Δ G).
• Bioenergetics is a field of biochemistry concerned with the transformation and use of energy by living cells and determining the direction and extent to which biochemical reactions occur.
• The Δ G°’ of a redox reaction is calculated as Δ G°’= - nF Δ E°’, where F ( Faraday’s constant) = 96.485kJ/mol - V = 23.06 kcal/mol - V.
• Bioenergetics provide rules upon which metabolism functions.
• Enthalpy (Δ H) is a measure of the change in heat content of the reactants and products, according to the first law of thermodynamics.
• If [reactants] = [products], Δ G = Δ G°’.
• Gibbs’ Free energy (Δ G) is the energy available to do work, calculated as Δ G= Δ H – T Δ S; temperature in Kelvin (+273.15).
• Standard Reduction Potential, E°, is the tendency of a substance to gain electrons and cause oxidation of another substance, with more positive the value of E°’, the more tendency to gain electrons and be reduced.
• If at equilibrium ( Δ G = 0), Δ G°’ = RT ln K eq.
• Biomolecules can be synthesized and degraded for some specialized cellular functions.
• Co-enzymes function in a way that metabolism becomes more economically manageable and comprehensive.
• Co-enzymes play role in fuel oxidation, reductive biosynthesis, and transfer of small fragments.
• • Co-enzymes are not enzymes, but they act as activated carriers in metabolic reactions.
• Overall/ Net Potential, E°’, is the sum of potentials of half reactions, E°’ = E°’red’n + E°’oxd’n.
• The ATP cycle is a crucial part of cellular respiration.
• Glycolysis and fatty acid oxidation are pathways in the production of Acetyl CoA.
• Chromatophores are the energy currency of the cell, powering most cellular work and hydrolytic cleavage of high energy phosphate bonds is coupled with an energy-requiring (non-spontaneous) reaction.
• Coupling of reactions is a process in cellular respiration.