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53 Cards in this Set

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  • Back
where is most of the energy of glucose conatined?
in pyruvate
4 options of pyruvate
1) Lactate
2) Acetyl- CoA
3) OAA
4) Alanine
where is alanine formed from pyruvate?
cytosol
where is lactate formed from pyruvate?
cytosol
where is OAA formed from pyurvate?
mitochondrial matrix
where is Acetyl-CoA formed from pyruvate?
mitochondrial matrix
Which two fates of pyruvate are irreversible?
OAA and Acetyl-CoA
what can pyruvate be oxidized to only in microbes?
acetaldehyde- ethanol.....releases NADH
Where does the potential engegy of glucose remain?
in Pyruvate and in the two NADH's from Glyceraldehyde 3-P Dehydrogenase
What is the factor determining the fate of pyruvate?
Oxygen availablilty!!!!!!
2 helpful things that occur when pyruvate-lactate
1)regenerates NAD+
2) lactate is transported back into the liver to form glucose by gluconeogenesis
what converts pyruvate to alanine?
L-glutatmate (amino group donar)
What is the fate of pyruvate in gluconeogenesis?
pyruvate- PEP
pyruvate- PEP is NOT energetically favorable....two steps required to overcome energy barrier
1)pyruvate- OAA
2) OAA-PEP
What happens to pyruvate when oxygen is plentiful?
forms Acetyl CoA
what is one of the most important IRREVERSIBLE steps in metabolism?
WHY?
Pyruvate- Acetyl CoA
can no longer be used to make glucose
is the concentration of Pyruvate or Lactate higher in cell?
Lactate concentration is MUCH higher
overall reaction of Alanine Aminotransferase
Pyruvate + NADH +NH3 = Alanine + NAD+
what donates amino group to Pyruvate to form Alanin?
Ll-Glutamate..... gets oxidized to alpha ketoglutarate
Pyruvate oxidized/or reduced when forms Lactate?
Reduced because you can see that NADH gets oxidized to NAD+
what is the additional good thing that occurs due to formation of alanine from pyruvate?
NH3 (toxic) gets converted into a derrivative that can be safely transported back to the liver
Enzyme that catalyzes reaction of pyruvate to lactate
Lactate Dehydrogenase
Important Points from Lactate Dehydrogenase Reaction
NAD+ is getting reduced

1) H goes as Hydride (H-) from NADH to C2 of Pyruvate (pyruvate gets reduced)
2) adds to carbonyl group and makes lactate
3)the reaction is STEREOSPECIFIC (which side o NADH ring loses H-)
4)ARGININE and HISTIDINE residues aid in catalysis
which aa residues help in catalysis of Lactate Dehydrogenase Rxn?
ARGININE AND HISTIDINE
Where is Pyruvate Dehydrogenase Complex located?
In the mitochondria
Three protiens that make up the enzyme Pyruvate Dehydrogenase Complex?
1) Pyruvate Dehydrogenase
2) Dihydrolipoyl Transacetylase
3) Dihydrolipoyl Dehydrogenase
cofactor of Pyruvate Dehydrogenase (E1)
TPP
cofactor of Dihydrolipoyl Transketolase
Lipoamide
cofactor of Dihydrolipoyl Dehydrogenase
FAD
vitamin of FAD
riboflavin
What is the overall goal of Pyruvate Dehydrogenase Complex?
To convert Pyruvate to Acetyl CoA
Pyruvate---> Acetyl CoA + ?
CO2 (has one less carbon than Pyruvate)
what is the role of TPP in Pyruvate Dehydrogenase?
transfers a 2C unit to Lipoamide
what is released during TPP reaction?
CO2
What is the role of Lipoamide?
Has a long swinging arm that brings the 2C piece to CoA, forming Acetyl CoA
what hapens to Sulfurs in presence of Lipoamide?
Disulfur (SH-SH) gets reduced to a dithiol
(S-S).
What happens in the Dihydrolipoyl Dehydrogenase reaction?
Two electrons are taken out...flavin gets reduced....NAD+ gets reduced to NADH....(in order to oxidize dithiol back to disulfide)
Two ways energy is captured by Pyruvate Dehydrogenase Complex
!)Acetyl CoA
2) NADH
what are inhibitors of the Pyruvate Dehydrogenase Complex?
Acetyl CoA, NADH AND ATP
what inactivates the Pyruvate Dehydrogenase Complex? How?
Pyruvate Dehydrogenase Kinase

Phosphorylation makes it INACTIVE
What are things that activate the Pyruvate Dehydrogenase Complex?
Insulin in adipose tissue....wants to take up glucose and use Acetyl CoA to make fatty acids!!
What is Beriberi?
Deficiency in Thiamine
how is Beriberi measured?
transketolase
what are found in very high levels of patients with Beriberi?
pyruvate and alpha ketoglutarate
what is sydrome in alcoholics due to thiamine insufficiency?
Wernike- Korsakoff Syndrome
what is always the substrate for TPP?
ketone
what does TPP transfer?
activated aldehyde groups
4 reactions requiring Thiamine
1) Pyruvate Dehydrogenase Complex
2) Transketolase (PP Pathway)
3) alpha-Ketoglutarate Dehydrogenase (TCA cycle)
4) one more in catablism of aa's
What enzyme transforms Pyruvate to OAA?
Pyruvate Carboxylase (Same as in gluconeogenesis)....ATP is split
cofactor for Pyruvate Carboxylase?
biotin
what does biotin do?
where does it work?
installs C02 on a molecule
pyruvate +C02 = OAA
Pyruvate Decarboxylase requres what cofactor?
TPP
How is usage of TPP in Pyruvate Decarboxylase different than usage in Pyruvate Dehydrogenase Complex?
1) no oxidation/reduction
2) no NAD/NADH part to it
3) no Flavin part