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24 Cards in this Set
- Front
- Back
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What is important about the TCA cycle?
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It is a mitochondrial pathway
It can completely oxidize acetyl-CoA to CO2 and H2O It yields high energy in the process |
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When is pyruvate dehydrogenase regulated?
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When providing substrate (acetyl-CoA) for TCA cycle
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What reaction takes place at PDH?
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Oxidative carboxylation of pyruvate to Acetyl-CoA and reduced electron carriers
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Which four enzyme in the TCA cycle produce reduced electron carriers?
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Isocitrate Dehydrogenase
Alpha-ketoglutarate dehydrogenase Succinate Dehydrogenase Malate Dehydrogenase |
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What reaction does Isocitrate Dehydrogenase catalyze?
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Isocitrate -> Alpha-ketoglutarate
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What reaction does alpha-ketoglutarate dehydrogenase catalyze?
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alpha-ketoglutarate -> Succinyl-CoA
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What reaction does succinate dehydrogenase catalyze?
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Succinate -> Fumarate
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What reaction does Malate dehydrogenase catalyze?
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L-Malate -> OAA
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Which TCA cycle enzyme produces GTP?
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Succinate Thiokinase
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Why can fat not create net glucose?
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2 carbons go into TCA cycle and 2 carbons come out (no net gain of carbon)
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What are the three important roles of TCA cycle?
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yield reduced electron carriers
yield carbon structures which can produce more complex structures Anapleurosis |
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What is Anapleurosis?
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Allowing intermediates to "fill up" the pathway
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What is the purpose of PDH?
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to provide substrate for the TCA cycle
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What is PDH?
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pyruvate dehydrogenase
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What are the activators of PDH?
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dephosphorylation
insulin in adipocytes catecholamines in cardiac muscle |
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What are the inhibitors of PDH?
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phosphorylation
acetyl-CoA NADH |
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What enzyme phosphorylates PDH?
what is the effect of phosphorylation? |
PDH kinase
effect - inhibition |
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What enzyme dephosphorylates PDH?
what is the effect of dephosphorylation? |
PDH phosphatase
effect - activation |
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What are the activators for PDH kinase?
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NADH
ATP acetyl-CoA |
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What are the inhibitors of PDH kinase?
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pyruvate
NAD+ CoASH ADP Ca2+ |
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What are the activators of PDH phosphatase?
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Mg2+
Ca2+ |
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Why is Ca2+ an important activator of PDH phosphatase?
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when alpha-adrenergic receptors are stimulated (especially in skeletal muscles), Ca2+ is released into the cytoplasm and stimulates a twitch
since energy is necessary for a twitch, PDH phosphatase should be activated so that it can activate PDH |
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Why is TCA cycle important for amino acids?
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acts as an entry point for many amino acids into energy production or gluconeogenesis
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when is PDH activated?
when is it inhibited? |
activated in low energy situations or under insulin signal
inhibited under high energy conditions or under glucagon signal |
