Fates of pyruvate Flashcards
What are the major metabolic fates of pyruvate?
Pyruvate can be converted into:
1)Lactate in anaerobic conditions.
2) Acetyl-CoA for entry into the citric acid cycle.
3) Oxaloacetate for gluconeogenesis or the citric acid cycle.
4) Alanine through transamination.
draw pyruvate
What role does pyruvate play in the Cori Cycle?
In the Cori Cycle, lactate produced by anaerobic glycolysis in muscles is transported to the liver, where it is converted back to pyruvate and then into glucose through gluconeogenesis
What is the role of lactate in anaerobic metabolism?
In anaerobic conditions, pyruvate is reduced to lactate to regenerate NAD+, which allows glycolysis to continue producing ATP when oxygen is limited
how is excess lactate production by the muscle cells dealt with?
in the cori cycle
-lactate is taken to the liver to be converted to glucose
what cells always produce lactate? why?
RBC’s because they lack mitochondria
what 2 pathways is oxaloacete an intermediate in?
CAC and gluconeogenesis
what enzyme converts pyruvate to lactate? what does the direction of the rxn depend on?
lactate dehydrogenase (LDH)
-depends on the [P/R]
why can’t lactate be used as fuel in the muscle cells during anaerobic conditions?
in aerobic conditions, lactate would build up and rxn would go in reverse (generating pyruvate and NADH) there is no way to reduce NADH as the ETC will not be working in anaerobic conditions
Why does transport of lactate cause decreases in pH?
because it it transported with H+
what transporter transfers lactate out into the bloodstream?
H+ linked monocarboxylate transporter
explain metabolically why people who excercise more are better at handling lactate metabolism?
exercise increases transription of the gene that produced the transporter respondible for lactate transport
how does pH changes from lactate production affect oxygen affinitty for Hb?
affinity of O2 for Hb decreases when pH decreases
-H+ binds to the heme group in Hb which stabilizes the T state and increases the ability for 2,3BPG to bind (causing O2 affinity to decrease)
how efficient is glycolysis (in a percent) ?
31%
what is the overall rxn from glucose to lactate?
where does the conversion of pyruvate to lactate occur?
cytosol
how does pH change from the prodcution of lactate in the blood cells vs muscle cells?
decreased pH in blood cells and increased pH in muscle cells
when lactate is converted to pyruvate what kind of metabolic reaction is this?
oxidation
during the cori cycle, where does the energy needed to synthesize glucose in the liver come from?
from the oxidation of fatty acids
where does the oxidation of pyruvate to acetyl coA occur?
mitochondrial matrix
how is pyruvate transferred from the cytosol to the mitochondrial matrix?
1) transfer across outer mitochondrial membrane
2) transefer across inner mitochondrial membrane using pyruvate translocase
what kind of transporter is the pyruvate translocase? what does this mean in terms of how it transports glucose?
H+ linked monocarboxylate transporter
-uses a H+ to transport pyruvate
what 3 types of reactions occur during the conversion of pyruvate to acetyl coA?
1) oxidation
2) Decarboxylation
3) Transacetylation
what 5 cofactors are present in the PDH complex? how are they differentiated?
Loosley bound: CoA and NAD+
-leave as NADH and Acetyl-coA
Tightly bound: TPP, Lipoamide, FAD
