dietary carbs II Flashcard

under anaerobic conditions, pyruvate is converted to _______ in a rxn catalyzed by _____which also releases ______ and is carried to the liver to form glucose
lactate, lactate dehydrogenase, NAD+
NADH/NAD+ is usually found in the cell in which form? what about ATP/ADP/AMP?
NADH and ATP are the more prevalent forms of each
if levels of NAD+ are high, what will happen to the anaerobic conversion of pyruvate?
the pyruvate -> lactate pathway will stop
how is pyruvate converted to a protein? (2 ways)
alanine aminotransferase adds an amino group to pyruvate, creating alanine. or pyruvate carboxylase converts pyruvate to oxaloacetate, (which can then be converted to other proteins)
where does glycolysis take place? TCA?
cytosol, mitochondria
how is pyruvate brought from the cytosol to the mitochondria?
pyruvate is brought from the cytosol to the mitochondria by the monocarboxylate transporter.
what kind of transporter is the monocarboxylate transporter? what is its driving force?
antiporter, it pumps out a negative OH- which is balanced by the pyruvate, which gives off a H+, therefore the driving force is the electro-chemical potential
why is the conversion of pyruvate to acetyl CoA considered an “oxidative decarboxylation”?
pyruvate donates an electron to NAD+, creating NADH, (oxidation). and the 3 carbon pyruvate gives off a CO2 in becoming the 2 carbon acetyl CoA, (decarboxylation)
which pathways are the “B” vitamins closely related to? what is FAD derived from? NAD+?
metabolic. vitamin B2, B3
what vitamin is involved with the catcholemines?
vitamin C
of the 5 enzymes involved in the pyruvate dehydrogenase complex, which are just regulators?
PDH kinase and phosphatase
of the 5 enzymes involved in the pyruvate dehydrogenase complex, which are the 3 that are directly involved in enzymatic activity?
pyruvate dehydrogenase, dihydrolipoyl transacetylase, and dihydrolipoyl dehydrogenase
what are the 5 cofactors involved with the PDH complex?
thiamine pyrophosphate, lipoic acid, coenzyme A, FAD- and NAD+
what step does the pyruvate dehydrogenase component of the PDH complex catalyze, and what prosthetic group does it utilize?
the pyruvate dehydrogenase component decarboxylzes pyruvate, utilizing thimine pyrophosphate, (TPP, vitamin B1)
what step does the dihyrolipoyl transacetylase component of the PDH complex catalyze, and what prosthetic group doe it utilize?
the dihyrolipoyl transacetylase component transfers the acetyl group to coenzyme A by passing it along the arms of a lipoamide, (attached to a lysine)
what step does the dihydrolipoyl dehydrogenase component of the PDH complex catalyze, and what prosthetic group does it utilize?
transfer of electrons to NAD+, using FAD, (vit B2)
what are the two main molecules that come together to make acetyl CoA? what are 2 important side products?
CoASH and pyruvate. NADH and CO2 are also produced.
what 3 major components make up acetyl CoA?
adenosine 3′ monophosphate, pantothenic acid, (vitamin B5), and a free sulfhydryl (-SH) group
what are other 2 similar reactions to that which the PDH complex catalyzes 1) in the TCA cycle and 2) in branched chain amino acid processing? what are the implications of these connections.
the alpha ketoglutarate dehydrogenase enzyme in the TCA cycle is similar, but only uses E1-3 and the cofactors. alpha keto acid dehydrogenase complex is also similar to PDH, but is used for oxidative decarboxylation of branched chain amino acids. therefore, any deficiency of these enzymes or cofactors will affect all 3 pathways
what is the first level of PDH complex regulation? is it more local or global regulation?
all three substrates are activators, 2 of the 3 products are inhibitors, (CO2 diffuses too quickly to have an effect) this is mostly local regulation
what is the second level of regulation for the PDH complex?
the two regulatory enzymes, PDH kinase phosphorylates to inactivate PDH, PDH phosphatase dephosphorylates, leading to activation of PDH
what is the third level of regulation of the PDH complex?
allosteric regulation of the 2 PDH regulatory enzymes. the substrates, (along with ADP), of the PDH complex inactivate the PDH inactivating kinase, and the products activate it. Mg2+ and Ca2+ also activate the PDH activating phosphatase.
what is the main function of PDH regulation?
to support the TCA cycle
what are 2 examples of uniporters?
Ca+ pump, ATP synthetase
what are symptoms of PDH deficiency?
high pyruvate, lactate, alanine levels. chronic lactic acidosis. severe neurological defects, possibly fatal
what are 2 tx options for PDH deficiency?
diet with less carbs, and dichloroacetate, (PDH kinase inhibitor)
which intermediate of glycolysis does the pentose phosphate pathway start from?
glucose 6 phosphate
what products are produced from glucose 6 phosphate reacting with 2NADP+ as catalyzed by G-6-P dehydrogenase, and 6-phosphogluconate dehydrogenase?
ribulose 5-phosphate, NADPH, and CO2
what uses can be applied for NADPH? ribulose 5-phosphate?
fatty acid synthesis, glutathione reduction. ribulose 5-phosphate can be converted to ribose 5-phosphate nucleotide biosynthesis
are either the oxidative or non-oxidative reactions of the PPP reversible?
yes, the oxidative is reversible
what 2 enzymes are involved in the non-oxidative portion of the PPP?
transketolase (C2 unit) and transaldolase (C3 unit)
what 2 molecules does the non-oxidative PPP eventually produce that link back to glycolysis?
F-6-P and glyceraldehyde-3-phosphate
how is the PPP regulated?
NADPH is an inhibitor of G-6-P dehydrogenase. also high insulin levels after a meal can induce liver G6PD
what is the genetic inheritance of G6PDH deficiency? what are it’s symptoms?
G6PDH deficiency is X linked. (fyi most common human enzyme defect). if low NADPH levels, erythrocytes are at risk of hemolytic anemia, induced by oxidative stress

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