Download Pyruvate Oxidation

Pyruvate Oxidation
SBI 4U
September 25th
Major Players in Pyruvate
Oxidation
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Pyruvate: leftover from glycolysis
NAD: Nicotinamine Adenine
Denucleotide  co-enzyme that carries
electrons from one reaction to another
CoA  coenzyme A.  Aids with the
oxidation of pyruvate
Acetyl-coA  central molecule in energy
metabolism
Major Players in Pyruvate
Oxidation
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NADH: Chargeless, hydrogenated form of
NAD. Important for stimulating ATP
production
Hydrogen
Carbon Dioxide
Pyruvate Oxidation
2 pyruvate + 2NAD + 2CoA  2acetyl-CoA + 2NADH + 2H + 2CO2
Pyruvate Oxidation in the Matrix
Pyruvate Oxidation: In a Glance
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Occurs in the inner membrane of the mitochondria
Occurs in 3 easy steps:
1) Pyruvate is oxidized (carboxyl [COOH] group
removed as Carbon dioxide) Carbon dioxide is
released as a result
2) Remaining 2 carbon group is oxidized by NAD+
and becomes an acetic acid (acetate) group. NAD+
gains 2 H atoms forming NADH
3) Coenzyme A attaches to acetate, forming acetylcoenzyme A
1st & 2nd Steps of Pyruvate
Oxidation
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First, a carboxyl group is removed from each of the pyruvate
molecules  CO2 released
Second, the remainder of the pyruvate molecules are oxidized
by NAD+ (lose electrons). Therefore NAD+ gains electrons
and 2 hydrogen atoms
Remaining pyruvate molecules (have two carbon compounds)
become an acetate group
Last Step of Pyruvate Oxidation
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A sulfur-containing compound called
Coenzyme A attaches to acetate, forming
acetyl-coenzyme A
All nutrients, whether protein, lipid or
carbohydrate, are converted to acetyl-CoA
and then channelled toward fat production
or ATP production, depending on the
organism’s immediate energy needs
Pyruvate Oxidation, continued…
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If ATP levels are high, acetyl-co A will be
directed into synthesis of fatty acids for
long-term energy storage
If ATP is needed, acetyl-co A is directed to
the next part of cellular respiration: The
Krebs Cycle
The Krebs Cycle (Citric Acid Cycle)
At a Glance
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8-step process  each step catalyzed by a different
enzyme
Product of 8th reaction  oxaloacetate is a reactant
in the first reaction (cycle)
Takes the pyruvate (3 carbons) and breaks it down,
all 6 carbon and oxygen atoms end up in CO2 and
H2O
Hydrogens and electrons are stripped and loaded
onto NAD+ and FAD to produce 6 NADH and 2
FADH which are transported to the final step
Krebs Cycle
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Each glucose molecule nets 2 pyruvic acids
(from earlier). The Krebs cycle breaks down
1 pyruvic acid at a time
Begins and ends with Oxaloacetic acid – a 4carbon molecule
Acetyl coA – product of Pyruvate Oxidation
is picked up by Oxaloacetic Acid in order to
convert it to citrate
Krebs Cycle, continued…
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This reaction converts the four-carbon
compound (Acetyl CoA) into a 6-carbon
compound (citrate)
NAD+ is reduced to NADH
ATP is formed by substrate-level
phosphorylation
Last 4 carbon atoms of the original glucose
molecule leave as fully oxidized CO2
moleculles