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34 Cards in this Set
- Front
- Back
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What does the fate of Pyruvate depend on?
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-cell energy charge
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If cell energy charge is low, what happens to pyruvate?
How about high? |
-oxidized to CO2 and H2O in the TCA cycle
-directed toward gluconeogenesis |
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Where does the enzymatic activities of the TCA cycle occur?
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-mitochondrion
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How is pyruvate directed toward gluconeogeneis when cell energy charge is high?
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-CoA is highly acylated (as acetyl-CoA)
-it allosterically activates pyruvate carboxylase which directs towards gluconeo. |
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How is pyruvate directed toward the TCA cycle when cell energy charge is low?
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-CoA NOT acylated
-pyruvate carboxylase remains inactive -pyruvate can then be metabolized via the PDH complex |
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What are the 5 coenzymes used in the PDH cycle?
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-CoA
-NAD+ -FAD+ -lipoic acid -thimaine pyrophosphate (TPP) |
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Which coenzymes are tightly bound to enzymes of PDH complex?
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-TPP
-lipoic acid -FAD+ |
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Which coenzymes are employed as carriers of products of the PDH cycle?
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-CoA
-NAD+ |
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What does PDH stand for and what role does it play in the TCA cycle?
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-Pyruvate Dehydrogenase
-oxidatively decarboxylates pyruvate so it can bind to TPP |
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What is the end result of the PDH complex and why is this important?
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-Acetyl-CoA
-this acts as regulation of the TCA cycle |
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How is Fluoroacetate a suicide substrate?
What is the purpose of this? |
-It becomes Citrate Synthase which then becomes Fluorocitrate
-this inhibits aconitase which blocks the TCA cycle |
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How many moles of ATP are generated from one mole pyruvate that enters the TCA cycle?
Give the breakdown of where the ATP comes from. |
-12 ATP
*3 mol NADH (1 mol is equal to 3 mol ATP) plus 1 mol FADH2 (1 mol equal to 2 ATP) plus 1 GTP (equal to 1 ATP) |
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Biosynthetically speaking, why is the TCA cycle important?
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-Each intermediate is important for other processes
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Biosynthetically, what is Actyl-CoA used for?
Alpha-ketoglutarate? Succinyl CoA? Oxaloacetate? |
-FA terpenoids
-AA -Porphyrins -Carb AA |
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What two cycles does the TCA cycle link?
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-glycolysis
-electron transport chain |
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Where is the TCA cycle regulated?
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-entry of Acetyl-CoA into cycle
-Isocitrate to alpha-ketoglutarate -alpha-ketoglutarate to succinyl-CoA |
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How is the first regulation site controlled?
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-high concenctrations of Succinyl-CoA and citrate act as allosteric inhibitors of citrate synthase stopping the conversion of citrate from OOA and Acetyl-CoA
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How is the second regulation controlled?
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-high concentrations of NADH and ATP inhibit cycle and therefor citrate synthesis (since this is a reversible reaction)
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How is the last regulation site controlled?
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-Succinyl-CoA and NADH inhibit formation of more Succinyl-CoA
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Overall, what affects PDH activity?
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-Its state of phosphorylation (most active in dephosphorylated state)
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What catalyzes phosphorylation of PDH and what effect does this have?
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-PDH kinase
-makes PDH less active since it is more phosphorylated |
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What enhances PDH kinase (and therefore phosphorylates PDH making it less active)?
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-high cellular charge which is indicated by increase in ATP, NADH, and aceyl-CoA.
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What inhibits PDH kinase?
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-increase in pyruvate
-ADP, NAD+, and CoASH |
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How is PDH phosphatase activated?
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-Mg2+ and Ca2+
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In adipose tissue, what increases PDH activity?
How about in cardiac muscle? |
-insulin
-catecholamines |
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What cycle is used in comparison to the TCA cyle in plants, some fungi, algae, protozoans, and bacteria?
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-Glyoxylate cycle
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Where does the glyoxylate cycle occur?
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-in glyoxysomes
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What is the purpose of the glyoxylate cycle?
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-using two carbon compounds (such as ethanol, acetate, and acetyl-CoA from FA) things can survive in the absence of photosynthesis by producing precursers of glucose.
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What are the intermediates of the glyoxylate cycle?
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-acetyl-CoA enters and becomes citrate
-then isocitrate -then glyoxylate (and succinate) -then malate -then oxaloacetate *repeats |
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What are some diseases of the TCA cycle?
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-Pyruvate Dehydrogenase Deficiency
-Fumarase Deficiency |
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Describe Pyruvate Dehydrogenase Deficiency
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-children have elevated serum lactate, pyruvate, and alanine
-neurological defects -treatment with dichloroacetate, inhibitor of pyruvate DH kinase |
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Describe Fumarase Deficiancy
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-rare
-urine contains elevated amounts of fumarate, succinate, ?-ketoglutarate, and citrate -severe neurological impairment and dystionia soon after birth |
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What are redox reactions composed of?
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-two half reactions which can be separated
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How can the energy change in a redox reaction be found?
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-separate reactions using table
-find potentials -plug into: change= acceptor - donor *donor has more negative potential so answer is positive |
