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26 Cards in this Set
- Front
- Back
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How is the Km of Glucokinase different from that of Hexokinase?
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Higher Km in glucokinase enzymes than hexokinase
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What are the important differences between glucokinase and hexokinase?
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1. Higher Km for GK than HK
2. GK not inhibited by G6P, but HK is (product inhibition) 3. GK is substrate specific for glucose, but HK is not (will act on any 6-carbon sugar) |
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What is the rate-limiting enzyme in glycolysis and gluconeogenesis?
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Phosphofructokinase-1 (PFK-1)
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What is important about Pyruvate Kinase?
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Pyruvate Kinase enzymes are tissue specific
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What kind of inhibition does PFK-1 experience?
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Non-competitive inhibition
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What molecules activate PFK-1?
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AMP
F2,6BP |
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What molecules inhibit PFK-1?
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ATP
Citrate |
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Where does citrate come from?
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Citrate is produced as a product of the TCA cycle, and moves into the cytosol via the action of a tricarboxylic acid transporter
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Why does citrate inhibit PFK-1?
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Citrate is produced by the TCA cycle, and an excess of citrate produces a high ATP/AMP ratio. this increased ratio limits the number of oxidized e- carriers, decreases rate of TCA cycle, increases [cit]mito, increases [cit]cyto
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What is the most potent activator of PFK-1?
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Fructose-2,6-bisphosphate
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What enzyme converts F6P to F2,6BP?
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Phosphofructokinase-2 (kinase domain)
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What enzyme converts F2,6BP to F6P?
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Phosphofructokinase-2 (Phosphatase Domain)
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When is Phosphofructokinase-2 expressing its phosphatase domain?
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when it's phosphorylated
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When is Phosphofructokinase-2 expressing its kinase domain?
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when it's dephosphorylated
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What is unique about PFK-2 (as compared to PFK-1)?
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PFK-2 can phosphorylate and dephosphorylate, whereas PFK-1 can only phosphorylate
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What is the role of PKA?
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It phosphorylates PFK-2
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What is the main inhibitor of F-1,6-BPase?
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F2,6BP
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What is the role of F1,6BPase?
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It dephosphorylates F1,6BP to F6P
It bypasses PFK-1 (glycolytic enzyme) for gluconeogenesis. |
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What role does pyruvate kinase serve?
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It is the terminal enzyme in glycolysis, converting PEP to pyruvate
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What are the activators for Pyruvate Kinase?
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F1,6BP
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What are the inhibitors of pyruvate kinase?
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ATP
Acetyl-CoA Phosphorylation by PKA Alanine |
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What is the mechanism that activates PKA?
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G-Protein Coupled Receptor
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What hormone activates the activity (causes the active form to be expressed) of PKA?
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Glucagon
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How does insulin combat the effects of the glucagon cascade?
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It decreases the amount of cyclic AMP (cAMP)
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What major glycolytic/gluconeogenic enzyme is phosphorylated by PKA?
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PFK-2
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How is PKA activated?
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cAMP binds to the two regulatory subunits and releases the two catalytic subunits to act
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