presentation source
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Electron Transport Chain
Filename: ETChain.ppt
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Lecture Outline
•
Using Chemical energy to drive metabolism
•
Production of ATP
•
Cellular respiration
–
Clycolysis
–
Krebs cycle
– Electron transport
– Chemiosmosis
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Lecture Overview
•
All organisms drive their metabolism with
ATP generated from
•
Rearrangement of chemical bonds
•
Energetic electrons from proton pumps
•
Electrons from photosynthesis
•
Electrons from oxidation of sugars and fats
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Cellular Respiration
•
Release of energy stored in organic compounds
–
Carbohydrate
–
Fats
–
Proteins (net energy loss)
•
Oxygen is consumed as a reactant
•
Carbon dioxide and water are byproducts
•
Energy is used indirectly
– trapped as ATP 4/10/2020
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Pathways in Cellular Respiration
•
Glycolysis
•
Krebs cycle
•
Electron transport chain
Cellular Respiration
Cumulative function of three metabolic pathways and chemiosmosis
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Catabolism of various foods
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A room of your own...
Overview of Cellular Respiration
ATP ATP
ATP
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Electron
Transport
System
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IN
Summary of Krebs Cycle
IN
Out
IN
Out
Out
Out
IN
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Electron Transport Chain
•
OCCURS in MITOCHONDRIAL INNER
MEMBRANE or PROKARYTOIC CELL
MEMBRANE
• linked to Glycolysis and Krebs cycle
•
Electrons passed from NADH to oxygen
•
Does not make ATP directly but through chemiosmosis
Large Free energy drop ( 53 kcal/mol) is broken into a series of smaller steps that release energy in manageable amounts
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Oxidation is the loss of electrons to any electron acceptor
Although oxygen is the usual electron acceptor other electron acceptors include
NAD+
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NADH as an Electron Shuttle
NAD H
Reduction
Oxidation
Nicotinamide-adenine dinucleotide
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Electron
Transport
Chain
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How ATP Drives Cellular Work
ATP
ATP ATP
ATP
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2 Ways to Produce ATP
•
Substrate level phosphorylation
– produces few molecules of ATP in aerobes (2
ATP from the respiration of 1 molecule of glucose)
•
Proton motor force (chemiosmosis)
– produces most of the ATP in aerobes (about 30
ATP from the complete respiration of glucose to
CO
2 and H
2
O)
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16 Substrate Level Phosphorylation
ATP Production
• more primitive method
Examples: 2 steps in glycolysis where
• ADP + Substrate-P -> ATP + substrate
• Note that the phosphate comes from a phosphorylated substrate, not from Pi
• 2 ADP + Phosphoenolpyruvate -> pyruvate + 2 ATP
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17 Proton Motor Force
ATP production
ATP synthase/ FoF1 complex
• More advanced method
• Proton transport across a membrane with F o
F
1 reaction:complex powers the following
• ADP + P i
-> ATP
• Note that the phosphate comes from P i
(inorganic phosphate)
• This is the major ATP source for aerobic bacteria, mitochondria and chloroplasts
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ATP synthase/ F
o
F
1
complex requires:
•
Membrane
•
Gradient of H+ concentration across membrane (one side more acid than the other)
•
Fo/Fi protein complex in membrane
•
ADP + Pi
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FoF1 complex
H
+
ADP ATP
+Pi
F1
Membrane low pH
H
+H
H
+
+
H
+
H
+
H
+ H
+
H
+
Fo
H
+
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FoF1 complex
H
+
F1 (9 protein subunits)
ADP
+Pi carries ATP synthase
ATP
Fo (3 subunits in bacteria) forms a proton channel
H
+
H
+
H
+
H
+
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FoF1 complexes under EM look like “ l o ll i p o p s ”
Fo
F1
Fo
F1 F1
Fo
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Dissociated FoF1
F1 Shows only ATP’ase
F1
F1
H
+
H
+
H
+
Fo Shows proton transfer Fo
H
+
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23 matrix
F
O
F
1
COMPLEXES
Aerobic bacterium
Mitochondrion
= acid region stroma
Chloroplast thylakoid
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How does the F o
F
1 complex work?
Not known
?
F1
Fo
One hypothesis is that F1 rotates as it releases ATP’s
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Chemiosmosis proton motor force chemical energy
ATP
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Review
Tally=2
Tally=0
Tally=2
Tally= ~36
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