MCAT chem1* – Flashcards

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-? H
+? S
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-? G, spontaneous at all temps
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+? H
-? S
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+? G, non-spontaneous at all temps
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-H
-S
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spont. at low temps
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+? H
+? S
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spont. at high temps
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if delta G is negative what does it tell you about energy and speed of rxn
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exothermic
cannot tell anything about how fast rxn is,
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-? G, then Keq
favors
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+Keq
products
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+? G, then Keq
favors
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-Keq
reactants
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G=0, then Keq
favors
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Keq=1
equilib
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Eqn for Gibbs free energy
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?G= ?H-T ?S
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Gibs energy eqn std in a cell where molarities arent 1
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? G*=-RTlnKeq
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catalyst
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lowers Ea in both directions by stabilizing Transition state
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what does catalyst do to equilibrium
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does not shift/mess with it
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higher Km means -- substrate
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lower affinity for S
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Km=
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1/2 vMax
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competitive inhibition
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inhibitor binds to active site
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competitive inhibition effect on Km and Vmax
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increases Km
doesn't change Vmax
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Non-competitive inhibition
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inhibitor binds not at active site
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non- competitive inhibition effect on Km and Vmax
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Km does not change
Vmax is lowered
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Cooperativity
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binding of one substrate increases affinity for the next substrate to bind
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cooperativity has a -- curve
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sigmoid
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Hb vs Mb
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Hb has 4, where Mb (muscle) only has 1 subunit and therefore Mb does not have cooperativity
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Bohr effect-
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prescence of H+ and CO2 decrease Hb affinity for O2 causing Hb to release O2 in the tissue. This shifts the sigmoid curve to the right
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Pressure of O2 is highest in
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lungs, causing the high % saturation of Hb to pick it up and deliver to tissue where PO2 is lower to release it
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allosteric regulation
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not active site, feedback inhibition
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phosphorylation
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covalent modification by adding a phosphate it adds - charge
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AA with an OH group that can be phosphorylated
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Ser, Thr, Tyr
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Kinases or phophorylations
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add phosphate
kinase- ATP hydrolysis
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phosphatases
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dephosphorylate enzymes, take phosphate off
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what does phosphorylation do to the enzyme
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changes the confirmation, either activating it or deactivating it.
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Zymogens
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inactive precursors that become active w/proteolytic cleavage
ex: digestive enzymes trypsin and chymotrypsin
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Cofactors
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enzyme regulation with the use of metal ions or coenzymes
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