Lecture 8 in Powerpoint format

298 k 25oc ph 7 and atmospheric pressure 1 atm temp it

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Unformatted text preview: mospheric pressure= 1 atm Temp= ***It is directly related to the Equilibrium Constant (K ’eq) ∆ G’o = -RT ln K’’eq -RT K If the system is at equilibrium in the presence of these starting If concentrations (forward rate = reverse rate) the ratio of the product of the concentrations of the products to that of the reactants is = 1 A+B↔ C+D K’eq eq = [C] [D] [A] [B] [A] Natural log of 1 = 0 Natural Thus ∆ G’o = 0 Thus Standard free energy change Standard (∆ G’o) The ∆ G’o values for sequential reactions are The additive so that individual reactions with an additive unfavourable (positive) ∆ G’o can move forward (reaction coupling). In biological systems the free energy of In hydrolysis of “high energy bonds” drives “high energetically unfavourable reactions energetically Recall: ∆ G’o = -RT ln K’eq Recall: -RT K’ Standard Free Energy Changes are Additive ATP + H2O ADP + Pi ∆ G’o = -30.5 kJ/mol -30.5 + Glucose + Pi Glu 6-P + H2O ∆ G’o = 13.8 kJ/mol ____________________________________________ _ Glucose + ATP Glu 6-P + ADP ∆ G’o = -16.7 kJ/mol Actual free energy change (∆ G) Actual Actual free energy change (∆ G) iis different s from standard free energy change (∆ G’ ). standard o Depends on actual concentrations of Depends reactants and products, temperature and pH pH ∆G = ∆ Go’ + RT ln RT [C] [D] [C] [A] [B] [A] High energy phosphagens High ATP: a common source of free energy for biological systems Hydrolysis of ATP to ADP and Pi has a ∆ G’o of -30.5 kJ/mol (actual ∆ G depends on microenvironment) This reaction MUST be coupled to another in order for the energy This to be used (and not released as heat) to Coupling involves the transfer of these groups from ATP to Coupling an enzyme or its substrate (“group transfer reaction”) an Thus, ATP has high “phosphoryl group transfer potential” Thus, “phosphoryl If you wanted to measure the ATP content of a cell or a tissue, how could you do this? The 2008 Nobel Prize winner in chemistry, Marine Biological Laboratory (Woods Hole, MA) scientist Osamu Shimomura, (L) receives his medal from the Swedish King Carl XVI Gustaf in Stockholm, Japanese-born Shimomura was awarded the Prize for the discovery and development of green fluorescent protein, GFP. Osamu Shimomura demonstrates the bioluminescence of the sea firefly, Cipridina, a small crustacean collected Cipridina small off the coast of Japan. Shimomura was the first person to purify the lightthe emitting luciferin molecule from Cipridina in 1956, an accomplishment that launched his scientific career. Cell or tissue extract Luciferin and Luciferase solution Measure amount of light Measure In Luminometer (e.g., multimode plate In reader) reader) Compare to light emitted from known amounts of ATP (i.e., a standard curve) In your sample. [ATP] unknown [ATP] What other molecules have high “group transfer potential”? “group GTP (has large negative ∆ G’ ) GTP PEP Glu 6-P Thioesters (e.g., acetyl CoA) Thioesters o However ATP remains However one of the most widely u...
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