Metabolism

• Metabolism is essential for sustaining life.
• Metabolism involves the exchange of energy between organisms and their environment.
• Metabolism is essential for life.
• ΔG of ATP hydrolysis is sufficiently negative to drive endergonic reactions.
• ΔG is a function of a reaction’s displacement from equilibrium.
• Gibbs energy changes (ΔG) predict if a reaction will occur spontaneously.
• Metabolism consists of catabolic pathways that break down nutrients into simpler substances, and anabolic pathways that build up simpler substances into complex ones.
• Metabolic maps contain much detail and can be used to describe major pathways such as Glycolysis, Tricarboxylic acid (TCA) cycle, Oxidative phosphorylation, Nutrient metabolism, and Energy conservation.
• ATP is the cell’s ‘energy currency’ and chemical energy is equal to ATP.
• Glucose is broken down in the following steps: Glycolysis, Oxphos, TCA, and ATP.
• The breakdown of one molecule of glucose to two molecules of pyruvate occurs in the Cytoplasm during Glycolysis.
• Activation in Glycolysis involves the conversion of Glucose to Fructose 1,6-Bisphosphate, Dihydroxyacetone Phosphate, and Glyceraldehyde 3-Phosphate.
• The pay-off in Glycolysis results in two ATP, two NADH, and two pyruvate.
• The tricarboxylic acid cycle, also known as the Citric acid cycle or Krebs cycle, occurs in the Mitochondrial matrix.
• In the tricarboxylic acid cycle, ATP is produced from Acetyl CoA and 8 electrons, resulting in 3 NADH and 1 succinate.
• Values are additive for coupled reactions: net ΔG < 0.
• Enzymes increase the rate at which reactions reach equilibrium but do not affect the equilibrium constant (K).
• ATP is not a 'high energy' compound and displacement of the mass action ratio from thermodynamic equilibrium allows ATP hydrolysis to drive other reactions.
• Metabolism allows energy exchange between an organism and its surroundings thus preventing decay into equilibrium.
• Energy cannot be made or destroyed and the entropy (disorder) of a system and its surroundings always increases.
• The mass action ratio and the equilibrium constant are different, as evidenced by mitochondria which can keep a mass action ratio that is 10 orders of magnitude lower than the equilibrium constant.
• Exergonic reactions are thermodynamically favourable and occur spontaneously, while endergonic reactions are thermodynamically unfavourable and require input of energy to occur.
• In isolation, reactions reach equilibrium when the net rate equals zero, which occurs only if a mechanism exists.
• The equilibrium constant (K) reflects the relative levels of reactants and products at equilibrium.
• ATP hydrolysis is associated with negative ΔG and mitochondria can keep a mass action ratio that is 10 orders of magnitude lower than the equilibrium constant.
• ΔG is negatively related to the overall entropy change of a system and its surroundings and is the thermodynamic driving force of a reaction.
• Coupled reactions involve endergonic reactions occurring when they are 'pushed' or 'pulled' by a coupled exergonic reaction, resulting in a net increase in entropy.
• The 1st law of thermodynamics states that energy cannot be made or destroyed, also known as the conservation of energy.
• The 2nd law of thermodynamics states that the entropy of a system and its surroundings increases and is maximal at equilibrium.
• The second law of thermodynamics states that the entropy of a system and its surroundings increases and is maximal at equilibrium.
• Glucose combustion yields ATP, also known as cellular respiration.
• Chemiosmotic coupling is a process that involves the coupling of chemical reactions with proton transport across the mitochondrial inner membrane.
• Mitochondrial protonmotive force (PMF) drives ATP synthesis.
• Metabolism, or change or exchange, is the exchange of energy between sunlight/food and biological structure.
• Burning food clearly liberates energy, but how can this energy be exploited for cell physiological purposes?
• Energy exchange is not 100% efficient, meaning that heat dissipation leads to a net increase in disorder.
• Organisms are open systems, meaning that building and maintaining an organism results in a net increase in entropy of the system and its surroundings.
• The rate of a chemical reaction is directly proportional to the product of the concentrations of each participating molecule, as stated by the law of mass action.
• Biological thermodynamics, also known as bioenergetics, is the study of the energy changes that occur in living organisms.
• ATP may be considered the cell’s energy currency.