TCA CYCLE Flashcards
What are anaplerotic(building up) reactions?
byosynthetic reactions proceeding from the TCA cycle require the input of carbons from intermediates othar than acetyl-coa.
what are the two major functions of the TCA cycle
production of energy and byosynthesis
T/F does the TCA cycle provides a common ground for interconversion of fuels and metabolites?
TRUE
succinyl coa serves as precursor to?
porphyrins(heme) in all cells , but especially in bone marrow and liver
the TCA cycle is a source of non essential aminocids such as ?
ASPARTATE AND GLUTAMATE
What was the first version of the TCA cycle , proposed by Krebs in 1937 ?
began with pyruvic acid , not acetyl coa
why the TCA cycle is described as amphibolic nature?
because of the catabolic(top) and anabolic(bottom) nature
coenzyme a is what kind of nucleotide?
adenine, containing panthogenic acid moiety and terminates in thiol group
where is the TCA cycle located ?
mitochondrial matrix
what is the main fate of mitochondrial acetyl coa?
oxidation in the TCA cycle , but in the cytoplasm it is used for biosynthesis of fatty acids and cholesterol.
mention the different metabolites that pyruvate can be converted to?
- lactate(lactate dehydrogenase)
- alanine ( alanine aminotranferase ALT)
- oxaloacetate (pyruvate carboxylase)
- acetyl coa (pyruvate dehydrogenase complex PDH )
Which enzyme is tetramer of identical subunits , each of which contains an allosteric site that binds acetyl coa , a positive heterotropic modifier?
pyruvate carboxylase
what complex serves as a bridge between carbohydrates and the TCA cycle?
pyruvate dehydrogenase complex (PDC)
What complex is one of the several alfa-ketoacid dehydrogenases having analogous reaction mechanisms, including alfa-ketoglutarate dehydrogenase in the TCA cycle and alfa-ketoacid dehydrogenases associated with the catabolism of leucine, isoleucine and valine ?
PDC COMPLEX
which 5 co enzymes are required for PDC activity?
- thiamine pyrophosphate
- lipoamide(lipoic acid bound in amide linkage to protein)
- coa
- FAD
- NAD+
which vitamins are required for synthesis of PDC complex?
- thiamine
- pantothenic acid
- riboflavin
- nicotinamide
deficiency of 1.thiamine 2.pantothenic acid 3. riboflavin 4. nicotinamide results in ?
beriberi due to thiamine deficiency
what are the symptoms of beriberi ?
cardiac and skeletal muscle weakness and neurologic disease.
what kind of vitamin is common in alcoholism?
thiamine
why is lactic acid measured in clinical setting?
because its accumulation can result in rapid death
why is lactic acid produced?
produced metabolically by the reversible reduction of pyruvate with NADH by the enzyme lactate dehydrogenase(LDH)
citrate synthase begins the TCA cycle by catalyzing the condensation of acetyl coa and oxaloacetate to form>
citric acid
which protein in the TCA cycle is an iron-sulfur?
ACONITASE
Aconitase is a two step reversible reaction and involves ?
dehydration followd by hydration
what is IRE-BP(Iron response element binding protein)
is a cytosolic protein with aconitasse activity and regulates iron storage
what is fluoroacetate?
potent toxin originally isolated from plants
fluoroacetylcoa + oxaloacetate =
fluorocitrate
what substance inhibits aconitase?
fluorocitrate
what is an example of a suicide substance?
fluoroacetate
what is a three point attachment?
citrate binds to the activate site of aconitase
citrate is an ________ molecule
achiral
why citrate is term a prochiral molecule?
because it is converted to achiral molecules , isocitrate
which substrate is an allosteric effector inhibiting in phosphofructokinase1 and activating acetyl coa carboxylase ?
citrate
T/F animals can perform net synthesis of glucose from acetyl-coa
FALSE
it is a process in which ADP is converted into ATP without involving the electron transport chain or oxidative phosphorilation?
substrate level phosphorylation
reactions catalyzed by phosphoglycerate kinase and pyruvate kinase in glycolysis uses also?
substrate level phosphorylation
the last 3 reactions on the TCA cycle illustrates a common theme in metabolism for introducing a carbonyl group into a molecule these are?
- introduction of a double bond
- addition of water across the double bond to form an alcohol
- oxidation of the alcohol to a ketone
which enzyme is a flavoprotein?
succinate dehydrogenase .. embedded in the inner mitochondrial membrane where it is a part of complex II( succinate Q reductase.
which enzyme adds water across the trans double bond of fumarate to form alfa-hydroxy acid, L-malate?
fumarase
clinical
-7 month child
-progressive neurologic deterioration characterized by loss of coordination and muscle tone
-unrelenting acidosis
tx: administration of thiamine had no effect
labs:
- elevated blood levels of lactate
-alfa-ketoglutarate
-branched-chain amino acids
postmortem
- gluconeogenic enzymes were shown to have normal activities
- pyruvate dehydrogenase and alfa-ketoglutarate dehydrogenase were deficient
-defective component show E1 , single gene component required by all of the alfa-ketoacid dehydrogenases
possible diagnosis?
leigh’s disease
what is leights disease?
group of disorders that are all characterized by lactic acidosis
T/F malate dehydrogenase reaction played an important role in elucidation of the cyclic nature of the TCA cycle?
TRUE
__________ It is a major regulatory enzyme within the TCA cycle. it is subject to allosteric inhibition by ATP and NADH and stimulation by ADP and NAD+
ISOCITRATE DEHYDROGENASE
what are the 3 TCA cycle enzymes described as tumor supressors because genetic defects in these enzymes are associated with human cancers ?
- succinate dehydrogenase
- fumarate hydratase
- isocitrate dehydrogenase
