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53 Cards in this Set

  • Front
  • Back
What is the fate of the electrons in NADH and FADH2 that gets made by the TCA cycle?
They donate the e- to th ETC
How many ATP are made per NADH and per FADH2 by oxidative phosphorylation?
What is the other source of ATP from the TCA cycle?
The GTP that is made at step #5 is converted by reaction with ADP to form ATP + GDP
What is the total energy generated by one round of the TCA CYCLE starting with 1 AcCoA?
12 ATP
What is the predominant factor that regulates the TCA cycle?
The cell's need for energy in the form of ATP
How does low cell ATP signal the TCA cycle to kick in more?
When ATP is low, ADP and Pi are high
What are 3 ways by which ADP stimulates the TCA cycle?
-Allosteric activation of Isocitrate dehydrogenase
-Accelerated ETC (results in)
-Increased NAD+
How does ample ATP slow down the TCA cycle?
NADH builds up and is a negative inhibitor of Isocitrate dehydrogenase.
What results from decreased Isocitrate dehydrogenase activity?
Isocitrate buildsup and pushes the equilibrium catalyzed by Aconitase in the Citrate direction
What is the result of buildup of Citrate?
Neg feedback inhibition of Citrate synthase.
What happens to oxaloacetate when NADH is high?
OAA is converted back to Malate
What are 3 vitamins required for reactions of the TCA cycle?
The Really Nice People
-Thiamine (TPP)
-Riboflavin (FAD)
-Niacin (NAD)
-Pantothenate (Coenzyme A)
What enzyme is necessary for generating AcCoA from glucose for entering into the TCA cycle?
Pyruvate dehydrogenase complex
Where is PDH found within the cell?
Only in the mito matrix
What is the reaction that the PDH complex catalyzes?
Pyruvate is oxidatively decarboxylated to form AcCoA
What are the 5 coenzymes and thus 4 vitamins needed for the PDH complex to function?
-TPP (Thiamine B1)
-Lipoic acid
-NAD (Niacin)
-FAD (Riboflavin B2)
-CoASH (Pantothenate B5)
What is a major contrast between the PDH complex and the similar enzyme a-KG dehydrogenase?
PDH exists in an inactive phosphorylated form, and is active when nonphosphorylated
What is responsible for phosphorylating the PDH complex?
A kinase that is associated with the multienzyme complex.
When is the Kinase active?
When products are high and want to feedback inhibit PDH activity
What molecules stimulate PDH Kinase phosphorylation?
When is the Kinase activity low?
When substrates are elevated, which decrease Kinase activity so PDH is nonphosphorylated and active.
So what are 3 molecules that inhibit PDH Kinase activity so that PDH is active?
-ADP does it too!
In addition to substrate inhibition of the PDH kinase, what can increase the activity of the PDH complex?
A phosphatase
What function does the TCA cycle serve in addition to transferring e- to NAD/FAD for the TCA cycle and oxidative phosphorylation?
Synthetic function!!
What are TCA cycle intermediates used for in the FASTING state? Where?
Production of Glucose in the Liver
What are TCA cycle intermediates used for in the FED state?
Fatty acid synthesis
In addition to making glucose and FA's, what are TCA cycle intermediates used for making?
Amino acids (or AA interconversion)
What are rxns that replenish TCA cycle intermediates as they are removed for Glucose/FA/AA synthesis called?
Anaplerotic reactions
What is a key enzyme that replenishes Oxaloacetate for the TCA? What substrate does it use?
-Pyruvate carboxylase
-Substrate is Pyruvate
What cofactor is utilized by Pyruvate carboxylase?
Biotin (B7)
What is Biotin commonly involved as a cofactor in?
CO2 fixation reactions
In what 3 tissues is Pyruvate carboxylase found? Where is it NOT found?
In: liver, brain, fat

NOT In: muscle
What is Pyruvate carboxylase activated by?
What are 4 things neeed for PC to work?
And what does Pyruvate carboxylase produce?
What is another substrate for anaplerotic reactions to replenish TCA intermediates?
Amino acids
What are 9 AA's that can be used in anaplerotic reactions?
What is GAV TIM PAT?
-Valine, Threonine, Ile, Met
-Phenylalanine, Tyr, Aspartate
What TCA intermediate does Glutamate get converted to?
And what 4 aa's can form Glutamate?
What TCA intermediate does Aspartate get converted to? How?
Oxaloacetate - by transamination
What aa can form Aspartate?
What TCA intermediate is formed from Valine, Threonine, Ile, and Methionine?
Succinyl CoA (via Propionyl CoA and methylmalonyl CoA)
What TCA intermediate is formed from Phenylalanine, Aspartate, and Tyrosine?
What TCA intermediates are used for gluconeogenesis?
Malate or Oxaloacetate
What precursors can form Pyruvate?
Alanine and Lactate
What converts Pyruvate to OOA to replenish it when OOA/Malate are removed for gluconeogenesis?
Pyruvate carboxylase
What TCA intermediate is used for Fatty Acid synthesis?
How does glucose get converted to citrate?
1. By PDH production of AcCoA
2. By PC production of OOA
What is the enzyme that catalyzes the anaplerotic reaction to replenish the TCA cycle intermediates?
Pyruvate carboxylase
How is Glucose and the TCA cycle involved in AA synthesis?
Glucose makes Pyruvate which gets converted to OAA by PC, then to amino acids..
What does OAA get transaminated to?
Aspartate and Asparagine
What 4 amino acids can be made from a-ketoglutarate?