Download Respiration: Occurs in two places in the cell Cytoplasm and

04-14-16: Lecture 6
Respiration: Occurs in two places in the cell
Cytoplasm
and mitochondria
Outer membrane
Inner membrane
cytoplasm
Matrix
Intermembrane space
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04-14-16: Lecture 6
Respiration: Occurs in 3 stages
Glycolysis “split sugars”
6C sugar
2 ● 3C sugars
(glucose)
(pyruvate)
Kreb’s cycle
redox
3C sugar
(pyruvate)
CO2 + NADH + FADH2
Oxidative Phosphorylation
NADH + FADH2
ADP + Pi
oxidized
NAD+ & FAD
ATP made
O2 is used (AEROBIC)
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04-14-16: Lecture 6
Respiration: Occurs in 3 stages
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04-14-16: Lecture 6
The RXNs of Respiration: Glycolysis
Glycolysis “split sugars”
6C sugar
2 ● 3C sugars
(glucose)
(pyruvate)
in cytoplasm
G3P
Glceraldehye-3-phosphate
High energy phosphate from ATP
2 Phases
Energy investment phase:
Energy payoff phase:
NET:
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04-14-16: Lecture 6
The RXNs of Respiration: Glycolysis
How is ATP made during Glycolysis?
Substrate level Phosphorylation
Transfer of phosphate from substrate directly to ADP
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04-14-16: Lecture 6
The RXNs of Respiration: Glycolysis
Energy investment phase
Energy payoff phase
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04-14-16: Lecture 6
The RXNs of Respiration: Glycolysis
What do I need to know about glycolysis?
Take place in cytoplasm
6C sugar
(glucose)
2 ● 3C sugars
(pyruvate)
(will go to Kreb’s cycle
in matrix of mitoch.)
2 Phases
Energy investment phase
Energy payoff phase
Key step: G3P (intermediate) is oxidized to reduce
NAD+ to NADH
ATP made by substrate level phosphorylation
Using kinases
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04-14-16: Lecture 6
The RXNs of Respiration: Entering the Krebs cycle
Pyruvate in cytosol
Oxidized as
it is transported
into mitoch.
Acetyl CoA
72 protein transport complex
1. Oxidation to release CO2
2. Reduction of NAD+ to NADH + H+
3. Coenzyme A linked to remaining 2 carbon sugar
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04-14-16: Lecture 6
The RXNs of Respiration: Krebs cycle (citric acid cycle)
CO2
3C
pyruvate
NAD+
NADH +
CoA
Acetyl-CoA
CoA
H+
NADH + H+
CO2
4C
NADH + H+
NAD+
6C
Citric acid
NAD+
5C
FADH2
4C
Energy Totals for Krebs
NAD+
FAD
NADH + H+
ATP
ADP
substrate level phosphorylation
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04-14-16: Lecture 6
The RXNs of Respiration: Glycolysis and Krebs Energy totals
Key products of Glycolysis
2 ATP
2 NADH + H+
2 pyruvates (3C sugar)
Key products of Krebs
2 ATP
8 NADH + H+
2 FADH2
Need to do to make ATP?
Need to regenerate NAD+ and FAD
Oxidative Phosphorylation
1. Electron transport: oxidation of NADH and FADH2 to NAD + and FAD
2. Chemiosmosis will generate ATP
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04-14-16: Lecture 6
The RXNs of Respiration: Electron Transport Chain
NADH + H+ + ½ 02  NAD+ + H20
ΔG << 0
Separate etransport them thru several proteins
Multiple small rxns
02 is ultimate acceptor of emultiple electron transport proteins involved
redox reactions – passed from 1 to the next
NADH enters at the beginning to donate its eFADH2 enters later (therefore FADH2 = 2/3 energy of NADH)
3 protein complexes pump e- from matrix into the intermembrane space
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04-14-16: Lecture 6
The RXNs of Respiration:
Electron Transport Chain
NADH + H+ + ½ 02  NAD+ + H20
ΔG = -53 kcal
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04-14-16: Lecture 6
The RXNs of Respiration: Electron Transport Chain
Chemiosmosis and the proton (H+) motive force
Linking e- transport and H+ shuttling to ATP synthesis
NADH + H+
FADH2
NAD+ + 2e- + 2 H+
FAD + 2e- + 2 H+
As e- enters the electron transport chain H+ are pumped across the
membrane (from matrix to intermembrane space)
NADH
FADH2
3 H+ complexes which generates – 3 ATPs made
2 H+ complexes which generates – 2 ATPs made
H+ now in high concentration in the intermembrane space
(2/3 energy of NADH –
because enters ETC later!)
H+ repel back into the matrix
Through the ATP synthase: channel which uses H+ gradient to make ATP
ADP + Pi
ATP
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04-14-16: Lecture 6
The RXNs of Respiration: Electron Transport Chain
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Show movie:http://vcell.ndsu.nodak.edu/animations/etc/movie.htm
04-14-16: Lecture 6
The RXNs of Respiration: ATP synthase
Linking e- transport and H+ shuttling to ATP synthesis
H+ gradient + ADP + Pi
ATP
Energy is generated from ion gradient
H+ ions: higher in the intermembrane space than in the matrix
Key is diffusion: spontaneous movement of a
molecule from high conc. to low conc.
H+ repel back into the matrix
But membrane is impermeable to H+ ions – so can’t get across
___________ is the one channel H+ ions can get back across
captures the energy of H+ movement down its conc. gradient to
make ATP
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The RXNs of Respiration: ATP synthase
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Show movie:http://vcell.ndsu.nodak.edu/animations/atpgradient/movie.htm
04-14-16: Lecture 6
The RXNs of Respiration: Energy totals
Krebs: matrix of mitochondria
2ATP + 8 NADH + 2FADH2
30 ATP total
substrate level
phosphorylation
24 ATP
4 ATP
Grand Total
36-38 ATPs
(3 per NADH) (2 per FADH2)
Glycolysis: cytosol
2ATP + 2 NADH
substrate level
phosphorylation
4 ATP
6 ATP
NADH made by glycolysis in the cytoplasm is
impermeable to membranes.
Its e- are passed to either NAD+ or FAD in
the Mitoch. via electron shuttling systems
Why 4 or 6 ATP?
Pay a toll of 2 ATPs if passed to FAD
FADH2
NAD+
NADH + H+
cytosol
e-
FAD
NAD+
50:50
chance
NADH +H+
Mitoch. matrix
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04-14-16: Lecture 6
Aerobic vs. Anaerobic Respiration
Aerobic requires O2:
Oxidative Phosphorylation
Need O2 to oxidize NADH and FADH2
(REDOX)
Normally:
Anaerobic does not requires O2:
Fermentation: In anaerobic conditions –
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04-14-16: Lecture 6
Fermentation: In anaerobic conditions – make NAD+
creak along on 2 ATPs per glucose
1Glucose (6C)
2 NAD+
2 NADH + H+
2ATP
2 Pyruvate (3C)
Anaerobic no O2
O2
 36-38
ATPs
Muscle
Yeast, bacteria
Lactic Acid
Ethanol
Recovery NAD+
Recovery NAD+
Get by on 2 ATPs per glucose!
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04-14-16: Lecture 6
Regulation of Respiration
Positive allosteric regulator
No O2  turn on fermentation
Feedback control
Negative allosteric regulators
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