Transcript Mitochondrion Pyruvate Oxidation & Kreb`s Cycle

MITOCHONDRIA
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Oval shaped organelles; randomly
scattered around the cytoplasm.
Energy factories of the cell; produce
the majority of the cell's ATP
 These ATP producing reactions
cannot take place without
oxygen, therefore the steps of
cellular respiration that occur in
the mitochondria are said to be
aerobic.
 Pyruvate Oxidation (Link
reaction), Krebs Cycle and the
Electron Transport Chain (ETC)
are all aerobic.
Eukaryotes use mitochondria to
produce cellular energy.
Prokaryotes do these reactions in
the cytoplasm and with much less
energy being produced.
MITOCHONDRIA
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The mitochondria are double-membraned
organelles.
 The folded inner membrane is known as
cristae. The cristae has many proteins
and other molecules embedded in it to
help with the process of cellular
respiration.
 The matrix is the protein rich fluid inside
the cristae.
 The fluid-filled space between the two
membranes is known as the
intermembrane (-ous) space.
Mitochondria have their own DNA, mtDNA,
and can therefore reproduce on their own.
This mtDNA is very similar to prokaryotic DNA
and has lead to the creation of the
endosymbiosis hypothesis which states that
mitochondria are descendants of early
prokaryotic cells who developed a symbiotic
relationship with early eukaryotic cells.
PYRUVATE OXIDATION
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The two pyruvates formed at the end of glycolysis are transported into the
matrix
In the matrix, under the control of a multi-enyzme, three changes occur.
 The carboxyl end is removed as carbon dioxide. This is known as a
decarboxylation reaction and is catalyzed by pyruvate decarboxylase.
 Pyruvate becomes oxidized into acetate and NAD+ is reduced to NADH
+ H+ (redox reaction)
 A sulfur-containing compound (coenzyme-A) is attached to the acetate,
forming acetyl-coA.
PYRUVATE OXIDATION
Co-A comes from vitamin B5 (pantothenic acid).
 The overall reaction:
2 pyruvate + 2NAD+ + 2 CoA --> 2 acetyl-CoA + 2NADH + 2H+ +
2CO2
 Acetyl-coA enters the Kreb cycle,
 NADH go to the electron transport chain to produce ATP
by oxidative phosphorylation
 Carbon dioxide diffuses out of the cell as a waste produt
 The protons (2H+) stay in the matrix.
 Acetyl-coA is the central molecule in energy metabolism.
The majority of macromolecules that we use for catabolism are
changed into acetyl-coA.
 Acetyl-coA can produce ATP or lipids. If you need energy you
get it as acetyl-coA enters the Krebs Cycle. If you do not need
energy then acetyl-coA is used to produce fat for energy
storage.
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KREBS CYCLE
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Founded by Hans Krebs
(biochemist at the Univ. of
Sheffield) in 1937. He won
the Nobel Prize in 1953 along
with Fritz Albert Lipmann who
discovered the importance of
coenzyme-A.
An 8-step process with each
step catalyzed by a specific
enzyme.
It is a cycle because the
product of step 8 is the
reactant in step 1
(oxaloacetate).
KREBS CYCLE
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By the end of the Krebs Cycle, the original glucose molecule is
consumed. The six carbon atoms have left as carbon dioxide
molecules.
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All that is preserved are 4ATP (two from glycolysis and two from
the Krebs Cycle) and 12 reduced coenzymes:
 2 NADH from glycolysis
 2 NADH from pyruvate oxidation
 6 NADH from the Krebs Cycle and
 2 FADH2 from the Krebs Cycle
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Most of the energy from glucose will be produced in the next
stage (ETC)