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24 Cards in this Set

  • Front
  • Back
What is important about the TCA cycle?
It is a mitochondrial pathway
It can completely oxidize acetyl-CoA to CO2 and H2O
It yields high energy in the process
When is pyruvate dehydrogenase regulated?
When providing substrate (acetyl-CoA) for TCA cycle
What reaction takes place at PDH?
Oxidative carboxylation of pyruvate to Acetyl-CoA and reduced electron carriers
Which four enzyme in the TCA cycle produce reduced electron carriers?
Isocitrate Dehydrogenase
Alpha-ketoglutarate dehydrogenase
Succinate Dehydrogenase
Malate Dehydrogenase
What reaction does Isocitrate Dehydrogenase catalyze?
Isocitrate -> Alpha-ketoglutarate
What reaction does alpha-ketoglutarate dehydrogenase catalyze?
alpha-ketoglutarate -> Succinyl-CoA
What reaction does succinate dehydrogenase catalyze?
Succinate -> Fumarate
What reaction does Malate dehydrogenase catalyze?
L-Malate -> OAA
Which TCA cycle enzyme produces GTP?
Succinate Thiokinase
Why can fat not create net glucose?
2 carbons go into TCA cycle and 2 carbons come out (no net gain of carbon)
What are the three important roles of TCA cycle?
yield reduced electron carriers
yield carbon structures which can produce more complex structures
What is Anapleurosis?
Allowing intermediates to "fill up" the pathway
What is the purpose of PDH?
to provide substrate for the TCA cycle
What is PDH?
pyruvate dehydrogenase
What are the activators of PDH?
insulin in adipocytes
catecholamines in cardiac muscle
What are the inhibitors of PDH?
What enzyme phosphorylates PDH?
what is the effect of phosphorylation?
PDH kinase

effect - inhibition
What enzyme dephosphorylates PDH?
what is the effect of dephosphorylation?
PDH phosphatase

effect - activation
What are the activators for PDH kinase?
What are the inhibitors of PDH kinase?
What are the activators of PDH phosphatase?
Why is Ca2+ an important activator of PDH phosphatase?
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
Why is TCA cycle important for amino acids?
acts as an entry point for many amino acids into energy production or gluconeogenesis
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