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10 Cards in this Set
- Front
- Back
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ATP hydrolysis can be coupled to and endergonic rxn to make that rxn happen. For example, an unfavorable reaction with a (delta) G of -------- could be driven (or fueled) by a mole of ATP?
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+5.5 kcal/mol: the delta G of ATP hydrolysis- an exergonic rxn- is -7.3 kcal/mole. ATP hydrolysis can be used to fuel an endergonic rxn- one with a positive delta G- that requires LESS THAN 7.3 kcal/mole.
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During coupling, HOW is ATP actually used to make a reaction happen?
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A phosphate is transferred to a reactant
phosphorylation is the basic mechanism by which ATP is used to do work. Either a REACTANT or a PROTEIN my be phosphorylated. In steps 1 and 3 of glycolysis, phosphorylation is used to boost energy of metabolic intermediate |
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How exactly does ATP drive the sodium-potassium pump?
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It transfers a phosphate to the pump
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Does allosteric regulation STIMULATE or INHIBIT an enzymes activity?
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it either stimulates or inhibits
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Isoleucine biosynthesis is regulated by FEEDBACK INHIBITION; and early step of its metabolic pathway is blocked at high concentrations of .........?
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Isoleucine
as the concentration of the final product increases, it binds more often to this enzyme, effectively shutting off the pathway from that point onward. The pathway will remain off until the products concentration drops again. Note that it is not always the first step of the pathway that is regulated, but merely an early step. |
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During feedback inhibition of isoleucine synthesis, which of the following molecule(s) stops being made?
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a) threonine , b) isoleucine, c) intermediate A ...........
Some, but not all of these answers are correct First, the product reaction is catalyzed by the deactivated enzyme ( in this case Intermediate A) stops being made. The remaining "A" will be converted to "B", and "B" will be converted to "C", and so on until all of these intermediates run out and isoleucine stops being made. As mentioned above, the pathway remains off until isoleucine becomes scarce again. |
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Regulation occurs through the enzyme threonine deaminase, whose activity is curtailed through.........?
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Non-competitive inhibition. (has an allosteric site in addition to it's active site)
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If activity of threonine deaminase is completely inhibited, would you expect greater concentrations of threonine to increase activity?
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NO, greater concentrations of threonine would not be able to outcompete the inhibitor, so inhibition would continue.
competition between the substrate and the regulatory molecule occurs when both molecules are capable of binding to the active site; this is known as competitive inhibition. |
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Threonine deaminase binds through --------- interactions?
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Weak interactions
Binding of threonine occurs at the active site of the enzyme. |
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How are lysosomal hydrolases localized within a cell?
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They are confined together within an organelle.
Confining hydrolytic enzymes to the lysosome both protects the cell from enzymes as well as ensures that the enzymes are only active within the lysosome ( and not for example in ER, where they are constructed). This is accomplished by controlling pH; the enzymes are most active at a pH of 5, and only the interior of lysosomes have a pH this low. |
