L4 - Pyruvate Dehydrogenase and TCA Cycle Flashcards
Feb. 6, 2019
Thiamine deficiency leads to what complications?
1) Wernicke-Korsakoff syndrome
2) wet beri-beri
What are the five enzymes of the pyruvate DHG complex?
1) pyruvate dehydrogenase
2) dihydrolipoyl dehydrogenase
3) dihydrolipoyl transacetylase
4) PDH kinase
5) PDH phosphatase
What are the molecules which activate PDH?
1) insulin
2) catecholamines
3) pyruvate
4) calcium
Where is the PDH complex found? Where does the TCA cycle occur?
PDH and TCA cycle occur in the mitochondrial matrix
What are the sources of Acetyl CoA?
From glucose through glycolysis.
From fatty acids through beta oxidation. From conversion of BCAAs.
Who are prone to thiamine deficiencies?
1) alcoholics
2) those with malnutrition
What is the enzyme which converts alpha-ketoglutarate into succinyl coA? What are the cofactors?
alpha-ketoglutarate. uses CoASH and NAD+
Phosphorylation of the PDH complex does what to the complex?
Inhibits it. Dephosphorylation will activate it.
What are the four molecules into which pyruvate can be turned into? Which reactions are irreversible? Reversible?
1) alanine (reversible)
2) acetyl coA (irreversible)
3) oxaloacetate (irreversible)
4) lactate (reversible)
How many NADH does the PDH complex make per pyruvate?
One NADH
What are the four regulated enzymes of the TCA cycle?
1) citrate synthase
2) isocitrate DHG
3) alpha-ketoglutarate DHG
4) succinate DHG
What are the molecules which inhibit PDH?
1) acetyl coA
2) ATP
3) NADH
What are the four major mitochondrial myopathies?
1) LHON
2) Kearns-Sayre syndrome
3) MELAS syndrome
4) MERRF syndrome
What are four functions of citrate?
1) source of cytosolic reducing equivalents
2) carbon source
3) regulator of metabolism
4) TCA cycle
What is produced through the reaction of succinyl CoA into succinate? What is the enzyme that catalyzes this reaction and what is another name for it?
1) GTP and CoASH
2) succinyl CoA synthetase
3) succinate thiokinase
Isocitrate is made from citrate through the actions of which enzyme?
Aconitase
What is the equivalents in ATPs for NADH? for FADH2?
NADH = 3 ATP FADH2 = 2 ATP
How many ATP (net) per glucose molecule are made in the TCA cycle?
12 (3 NADH, 1 GTP, 1 FADH2)
Which four intermediates of the TCA cycle can be made by conversion of amino acids?
1) oxaloacetate
2) fumarate
3) alpha-ketoglutarate
4) succinyl coA
L-malate turns into oxaloacetate through the actions of which enzyme?
malate DHG
Isocitrate DHG catalyzes a two-step reaction which turns what into what?
Isocitrate into alpha-ketoglutarate
What are three clinical manifestations of PDH deficiency?
1) lactic acidosis
2) myopathy
3) neurological defects
A high NADH/NAD+ implies which state? What happens with the TCA cycle?
1) implies high-energy state
2) inhibits TCA
How is the inner mitochondrial membrane as compared to the outer mitochondrial membrane?
Much more impermeable to molecules
What the main activators for enzymes in the TCA cycle? Main inhibitors?
Activators: ADP, calcium
Inhibitors: ATP, NADH, citrate
Succinate is turned into fumarate via ______, which is turned into ______ by the actions of _______.
1) succinate DHG
2) L-malate
3) fumarase
Which enzyme catalyzes the first proper step of the TCA cycle?
Citrate synthase
What are the five coenzymes of the PDH complex?
1) lipoic acid
2) NAD+ (derived from vitamin B3/niacin)
3) FAD (derived from vitamin B2/riboflavin)
4) CoASH
5) thiamine pyrophosphate (TPP)
Which molecule inhibits aconitase? Which one inhibits lipoic acid? Succinate dehydrogenase?
1) fluoroacetate inhibits aconitase
2) arsenic binds lipoic acid
3) malonate inhibits succinate DHG
Which enzyme converts pyruvate into alanine? Into lactate? Into acetyl coA? Into oxaloacetate?
Alanine: alanine aminotransferase
Lactate: lactate dehydrogenase
Acetyl CoA: pyruvate dehydrogenase
Oxaloacetate: pyruvate carboxylase
