L28: Energy and Metabolism

• What does Gibbs free energy indicate about a system?

  It tells us if a change to our system will happen spontaneously or not.
• What is the formula for Gibbs free energy?

  ΔG = ΔH - TΔS
• What does ΔG = 0 signify in a reaction?

  It indicates that there is no overall change and the system is at dynamic equilibrium.
• How do the concentrations of G-6-P and F-6-P affect the direction of the reaction?

  Increased [G-6-P] leads to formation of F-6-P, making ΔG negative.
• What does a large negative ΔG indicate about a reaction?

  It means the reaction is far from equilibrium and is irreversible under physiological conditions.
• What is the mass action ratio in a reaction A + B → C + D?

  The mass action ratio is q = [C][D]/[A][B].
• What does the mass action ratio tell us about a reaction?

  It measures how far we are from equilibrium conditions.
• What is the standard free energy change equation?

  ΔG = ΔG° + RT ln q
• What are the units for standard free energy change?

  J/mol or kcal/mol.
• What does it mean when ΔG = 0?

  No free energy change takes place, indicating the system is at equilibrium.
• How is the equilibrium constant related to standard free energy?

  ΔG°' = -RT ln K_eq.
• What does a small change in ΔG°' indicate about K_eq?

  Relatively small changes in ΔG°' can lead to big changes in K_eq.
• What is the conversion of dihydroxyacetone-phosphate to glyceraldehyde-3-phosphate?

  It is an example of a biochemical reaction.
• How do you calculate ΔG under specific conditions for the conversion of DHAP to G3P?

  Use the equation ΔG = ΔG°' + RT ln q.
• How do you calculate ΔG°' for the conversion of DHAP to G3P?

  Use the equation ΔG = ΔG°' + RT ln q.
• How do you calculate ΔG for the conversion of DHAP to G3P in vivo?

  Use the equation ΔG = ΔG°' + RT ln q with the given concentrations.
• Who discovered that ATP is the main energy carrier in the cell?

  Friz Lippman.
• What is the ΔG°' for the hydrolysis of ATP?

  ΔG°' = -30.5 kJ/mol.
• What role does adenylate kinase play in energy metabolism?

  Adenylate kinase interconverts ATP, ADP, and AMP.
• How much energy is released when ATP is hydrolyzed?

  ΔG°' = -30.5 kJ/mol under standard conditions.
• How is the actual ΔG calculated when ATP is not at equilibrium?

  ΔG = ΔG°' + RT ln q.
• What is the myth regarding ATP and energy bonds?

  It is a myth that ATP has high energy bonds compared to other bonds.
• What is the reaction that produces ATP?

  ADP + PO₄ → ATP.
• How much ATP does a cheetah use during a 10-second sprint?

  0.55 kg ATP or 3% of body weight for a small cheetah.
• How can K_eq be affected in biochemical reactions?

  K_eq can be affected by coupling reactions.
• What is the role of redox reactions in energy metabolism?

  They are used for storing and releasing energy during glycolysis and the citric acid cycle.
• What happens during a redox reaction?

  Oxidation involves a compound donating electrons, while reduction involves a compound accepting electrons.
• What does redox potential describe?

  It describes a compound's propensity to accept electrons.
• What is the overall redox potential for the reaction NADH + ½ O₂ → H₂O + NAD⁺?

  ΔE°' = 1.14V for the overall reaction.
• How is ΔG°' related to redox potential?

  ΔG°' = -nFΔE°' where n is the number of electrons and F is Faraday's constant.
• What does Gibbs free energy tell us about reactions?

  It tells us whether reactions are spontaneous and depends on enthalpy and entropy.