6-OHDA alters coupled respiration on isolated rat brain mitochondria
Wednesday, July 6, 2011lorenowicz.weebly.com/uploads/4/6/1/6/4616010/sbi4u-cellular... ·...
Transcript of Wednesday, July 6, 2011lorenowicz.weebly.com/uploads/4/6/1/6/4616010/sbi4u-cellular... ·...
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What is the fate of Pyruvate?
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GLYCOLYSIS
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PYRUVATE OX.
KREBS CYCLE
ETC
Stages of Cellular Respiration
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The Krebs Cycle – does your head suddenly hurt?
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The Krebs Cycle – An Overview
• In the presence of O2, the pyruvate of most cells enters the Krebs cycle (citric acid cycle), in which each pyruvate is oxidized to three molecules of CO2.
• 6 additional NAD+ molecules are reduced to 6 NADH, and 2 FAD+ (a second electron carrier) are reduced to form 2 FADH2.
• 2 additional ATPs are formed as the 2 pyruvates are oxidized in the Krebs cycle.
• The Krebs cycle occurs in the mitochondria of eukaryotic Wednesday, July 6, 2011
MitochondriaFunction• Mitochondria are cell
organelles.• They are often called the
powerhouses of the cell because they contain enzymes that help metabolize food into ATP.
• The ATP is generated through several oxidation reactions.
• All cells have different numbers of mitochondria. Cells that require a lot of energy usually have more.
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Structure• Mitochondria have two membranes: 1)outer membrane2)inner membrane that is folded into structures called cristae.
•The inner fluid of the mitochondria is called the matrix.•There are hundreds of enzymes in the matrix.
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Anatomy of the Mitochondria
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A
B
C
D
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• Pyruvate is oxidized in the mitochondria to produce acetyl-CoA and CO2
• This reaction is a link between glycolysis and the reactions of the Krebs cycle as acetyl-CoA is used by the Krebs cycle.
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The Krebs Cycle – Oxidation of Pyruvate (transition step)
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The Krebs Cycle – Oxidation of Pyruvate (transition step)
A 3 carbon molecule of pyruvate
enters the mitochondrion from the cytoplasm. One atom is removed via and hydrogen is removed using
carbondecarboxylation
NAD+.
Coenzyme A (CoA) becomes attached to the remaining
2 carbon atoms, creating Acetyl-CoA, which enters the
Krebs cycle.
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The Krebs Cycle – Oxidation of Pyruvate (transition step)
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What is the word reaction for pyruvate oxidation?
Pyruvate + NAD+ + CoA acetyl-CoA + NADH + CO2 + H+
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The Krebs Cycle
most enzymes for these rxns are located in mitochondrial matrix
8 steps w/ 8 dif. enzymes
oxaloacetate is recycled
cycle turns twice for every glucose molecule oxidized
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The Krebs Cycle
Acetyl-CoA enters the cycle and then combines with
oxaloacetate to make the 6-carbon compound citrate.
During the eight steps of the Krebs cycle, citrate undergoes
a number of reactions, releasing CO2 and ATP
in a number of steps. Citrate is eventually converted into
oxaloacetate so it can be used again during the Krebs cycle.
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The Krebs Cycle – The Products
1. is released as waste.
NADH and
respiration.
3. Energy is released in the form of ATP.
A glucose molecule produces two
because two molecules of
CO2
2. FADH2 move to the next stage of cellular
molecules of ATP.
pyruvate are created from
each molecule of glucose
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The Krebs Cycle
Used the diagram in the next panel to determine the products of the Krebs Cycle, both per each acetyl and glucose molecule: per acetyl molecule per glucose molecule ___NADH ___ NADH ____FADH2 ____ FADH2 ___ATP (subs. level) ____ ATP ___ CO2 ____ CO2
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How many oxidation reactions occur in Krebs? Where?
Where does the condensation reaction occur?
Where does the isomerization reaction occur?
Where does substrate-level phosphorylation occur?
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NADH and FADH2 transfer their electrons to the electron transport chain (ETC)
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LAST STEP!!! Electron Transport and Chemiosmosis
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The electron transport chain (ETC) Series of proteins arranged along the
inner membrane (the cristae) Increasing negativity Get a series of redox reactions
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Free energy released with each redox
Oxygen is the final electron acceptor
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ETC – the finer details NADH passes 2 electrons to NADH dehydrogenase Electrons are moved along the ETC
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ETC – the finer details Free E that is released is used to pump H+ from the
matrix intermembrane space For every pair of e-s, each protein pumps out one H+
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ETC – the finer details When oxygen is reduced, it also binds 2 H+,
and forms one H2O (inside the matrix)
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Chemiosmosis = ATP formation
Proton-motive force drives H+ through an ATPase complex. Free energy released.◦ Drives phosphorylation of ADP ATP
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Electrochemical (E.C.) gradient established across membrane by H+◦ High [H+] in intermembrane space
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Energy accountingOne ATP formed for every H+ that moves in
through ATPase
For each pair of e-’s, one H+ is pumped in by each of the three stationary proteins in the ECT.
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3 ATP for every NADH
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2 ATP for every FADH2◦ FADH2 passes its e-’s to cytochrome b-c1 complex
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Conversion (cashing out)3 ATP per NADH: 3 ATP x 8 NADH = 24 ATP
2 ATP per FADH2
2 ATP x 4 FADH2 = 8 ATP
= 32 ATP (ETC) + 4 ATP (glycol./Krebs)
total 36 ATP34
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Summary of processC6H12O6 + 6O2 6CO2 + 6H2O +
energy
Glucose is oxidized to carbon dioxide.
Oxygen is reduced to water.
36 molecules of ATP are produced.
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