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53 Cards in this Set
- Front
- Back
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What is the fate of the electrons in NADH and FADH2 that gets made by the TCA cycle?
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They donate the e- to th ETC
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How many ATP are made per NADH and per FADH2 by oxidative phosphorylation?
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NADH = 3 ATP
FADH2 = 2 ATP |
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What is the other source of ATP from the TCA cycle?
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The GTP that is made at step #5 is converted by reaction with ADP to form ATP + GDP
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What is the total energy generated by one round of the TCA CYCLE starting with 1 AcCoA?
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12 ATP
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What is the predominant factor that regulates the TCA cycle?
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The cell's need for energy in the form of ATP
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How does low cell ATP signal the TCA cycle to kick in more?
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When ATP is low, ADP and Pi are high
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What are 3 ways by which ADP stimulates the TCA cycle?
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-Allosteric activation of Isocitrate dehydrogenase
-Accelerated ETC (results in) -Increased NAD+ |
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How does ample ATP slow down the TCA cycle?
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NADH builds up and is a negative inhibitor of Isocitrate dehydrogenase.
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What results from decreased Isocitrate dehydrogenase activity?
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Isocitrate buildsup and pushes the equilibrium catalyzed by Aconitase in the Citrate direction
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What is the result of buildup of Citrate?
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Neg feedback inhibition of Citrate synthase.
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What happens to oxaloacetate when NADH is high?
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OAA is converted back to Malate
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What are 3 vitamins required for reactions of the TCA cycle?
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The Really Nice People
-Thiamine (TPP) -Riboflavin (FAD) -Niacin (NAD) -Pantothenate (Coenzyme A) |
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What enzyme is necessary for generating AcCoA from glucose for entering into the TCA cycle?
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Pyruvate dehydrogenase complex
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Where is PDH found within the cell?
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Only in the mito matrix
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What is the reaction that the PDH complex catalyzes?
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Pyruvate is oxidatively decarboxylated to form AcCoA
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What are the 5 coenzymes and thus 4 vitamins needed for the PDH complex to function?
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-TPP (Thiamine B1)
-Lipoic acid -NAD (Niacin) -FAD (Riboflavin B2) -CoASH (Pantothenate B5) |
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What is a major contrast between the PDH complex and the similar enzyme a-KG dehydrogenase?
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PDH exists in an inactive phosphorylated form, and is active when nonphosphorylated
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What is responsible for phosphorylating the PDH complex?
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A kinase that is associated with the multienzyme complex.
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When is the Kinase active?
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When products are high and want to feedback inhibit PDH activity
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What molecules stimulate PDH Kinase phosphorylation?
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-NADH
-AcCoA |
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When is the Kinase activity low?
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When substrates are elevated, which decrease Kinase activity so PDH is nonphosphorylated and active.
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So what are 3 molecules that inhibit PDH Kinase activity so that PDH is active?
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-NAD+
-CoAsh -ADP does it too! |
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In addition to substrate inhibition of the PDH kinase, what can increase the activity of the PDH complex?
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A phosphatase
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What function does the TCA cycle serve in addition to transferring e- to NAD/FAD for the TCA cycle and oxidative phosphorylation?
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Synthetic function!!
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What are TCA cycle intermediates used for in the FASTING state? Where?
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Production of Glucose in the Liver
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What are TCA cycle intermediates used for in the FED state?
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Fatty acid synthesis
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In addition to making glucose and FA's, what are TCA cycle intermediates used for making?
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Amino acids (or AA interconversion)
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What are rxns that replenish TCA cycle intermediates as they are removed for Glucose/FA/AA synthesis called?
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Anaplerotic reactions
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What is a key enzyme that replenishes Oxaloacetate for the TCA? What substrate does it use?
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-Pyruvate carboxylase
-Substrate is Pyruvate |
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What cofactor is utilized by Pyruvate carboxylase?
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Biotin (B7)
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What is Biotin commonly involved as a cofactor in?
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CO2 fixation reactions
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In what 3 tissues is Pyruvate carboxylase found? Where is it NOT found?
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In: liver, brain, fat
NOT In: muscle |
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What is Pyruvate carboxylase activated by?
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AcCoA
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What are 4 things neeed for PC to work?
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-Pyruvate
-CO2 -ATP -Biotin |
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And what does Pyruvate carboxylase produce?
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Oxaloacetate
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What is another substrate for anaplerotic reactions to replenish TCA intermediates?
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Amino acids
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What are 9 AA's that can be used in anaplerotic reactions?
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GAV TIM PAT
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What is GAV TIM PAT?
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-Glutamate
-Aspartate -Valine, Threonine, Ile, Met -Phenylalanine, Tyr, Aspartate |
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What TCA intermediate does Glutamate get converted to?
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alpha-Ketoglutarate
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And what 4 aa's can form Glutamate?
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GAPH
-Glutamine -Arginine -Proline -Histidine |
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What TCA intermediate does Aspartate get converted to? How?
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Oxaloacetate - by transamination
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What aa can form Aspartate?
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Asparagine
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What TCA intermediate is formed from Valine, Threonine, Ile, and Methionine?
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Succinyl CoA (via Propionyl CoA and methylmalonyl CoA)
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What TCA intermediate is formed from Phenylalanine, Aspartate, and Tyrosine?
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Fumarate
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What TCA intermediates are used for gluconeogenesis?
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Malate or Oxaloacetate
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What precursors can form Pyruvate?
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Alanine and Lactate
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What converts Pyruvate to OOA to replenish it when OOA/Malate are removed for gluconeogenesis?
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Pyruvate carboxylase
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What TCA intermediate is used for Fatty Acid synthesis?
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Citrate
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How does glucose get converted to citrate?
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1. By PDH production of AcCoA
2. By PC production of OOA |
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What is the enzyme that catalyzes the anaplerotic reaction to replenish the TCA cycle intermediates?
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Pyruvate carboxylase
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How is Glucose and the TCA cycle involved in AA synthesis?
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Glucose makes Pyruvate which gets converted to OAA by PC, then to amino acids..
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What does OAA get transaminated to?
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Aspartate and Asparagine
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What 4 amino acids can be made from a-ketoglutarate?
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GAPG
-Glutamate -Glutamine -Arginine -Proline |
