respiration: cytoplasmclasses.biology.ucsd.edu/bild1.sp16/lect-6-sv.pdf · nadh made by glycolysis...
TRANSCRIPT
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Respiration: Occurs in two places in the cell
Cytoplasm and mitochondria
cytoplasm Matrix
Inner membrane
Outer membrane
Intermembrane space
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Respiration: Occurs in 3 stages
Glycolysis “split sugars”
6C sugar 2 ● 3C sugars
(glucose) (pyruvate)
Kreb’s cycle
3C sugar CO2 + NADH + FADH2
(pyruvate)
redox
Oxidative Phosphorylation
NAD+ & FADoxidized
NADH + FADH2
ATP madeADP + Pi
O2 is used (AEROBIC)
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Respiration: Occurs in 3 stages
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The RXNs of Respiration: Glycolysis
Glycolysis “split sugars”
6C sugar 2 ● 3C sugars
(glucose) (pyruvate)in cytoplasm
G3P
Glceraldehye-3-phosphateHigh energy phosphate from ATP
2 Phases
Energy investment phase:
Energy payoff phase:
NET:
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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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The RXNs of Respiration: Glycolysis
Energy investment phase Energy payoff phase
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The RXNs of Respiration: Glycolysis
What do I need to know about glycolysis?
6C sugar 2 ● 3C sugars
(glucose) (pyruvate)
2 PhasesEnergy investment phaseEnergy payoff phase
Key step: G3P (intermediate) is oxidized to reduce NAD+ to NADH
ATP made by substrate level phosphorylationUsing kinases
Take place in cytoplasm
(will go to Kreb’s cycle in matrix of mitoch.)
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The RXNs of Respiration: Entering the Krebs cycle
Pyruvate in cytosol
Oxidized asit is transportedinto mitoch.
Acetyl CoA
72 protein transport complex1. Oxidation to release CO2
2. Reduction of NAD+ to NADH + H+
3. Coenzyme A linked to remaining 2 carbon sugar
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The RXNs of Respiration: Krebs cycle (citric acid cycle)
3Cpyruvate
NAD+NADH + H+
CO2
Acetyl-CoA
CoA
CoA
6CCitric acid
5C
4C
4CCO2
NADH + H+NAD+
NADH + H+
NAD+
ADPATP
substrate level phosphorylation
FAD
FADH2
NADH + H+
NAD+
Energy Totals for Krebs
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The RXNs of Respiration: Glycolysis and Krebs Energy totals
Key products of Glycolysis2 ATP2 NADH + H+
2 pyruvates (3C sugar)
Key products of Krebs2 ATP8 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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The RXNs of Respiration: Electron Transport Chain
NADH + H+ + ½ 02 NAD+ + H20 ΔG << 0
Separate e-transport them thru several proteinsMultiple small rxns02 is ultimate acceptor of e-
multiple electron transport proteins involvedredox reactions – passed from 1 to the next
NADH enters at the beginning to donate its e-
FADH2 enters later (therefore FADH2 = 2/3 energy of NADH)
3 protein complexes pump e- from matrix into the intermembrane space
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The RXNs of Respiration:
Electron Transport Chain
NADH + H+ + ½ 02 NAD+ + H20
ΔG = -53 kcal
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The RXNs of Respiration: Electron Transport Chain
Chemiosmosis and the proton (H+) motive force
NAD+ + 2e- + 2 H+NADH + H+
As e- enters the electron transport chain H+ are pumped across the membrane (from matrix to intermembrane space)
H+ now in high concentration in the intermembrane space
H+ repel back into the matrix
Through the ATP synthase: channel which uses H+ gradient to make ATP
ATPADP + Pi
NADH 3 H+ complexes which generates – 3 ATPs madeFADH2 2 H+ complexes which generates – 2 ATPs made
Linking e- transport and H+ shuttling to ATP synthesis
FAD + 2e- + 2 H+FADH2
(2/3 energy of NADH –because enters ETC later!)
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The RXNs of Respiration: Electron Transport Chain
Show movie:http://vcell.ndsu.nodak.edu/animations/etc/movie.htm
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The RXNs of Respiration: ATP synthase
Energy is generated from ion gradientH+ ions: higher in the intermembrane space than in the matrix
ATPADP + Pi
Linking e- transport and H+ shuttling to ATP synthesis
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 acrosscaptures the energy of H+ movement down its conc. gradient to make ATP
H+ gradient +
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The RXNs of Respiration: ATP synthase
Show movie:http://vcell.ndsu.nodak.edu/animations/atpgradient/movie.htm
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The RXNs of Respiration: Energy totals
Krebs: matrix of mitochondria
2ATP + 8 NADH + 2FADH2
24 ATP 4 ATP
30 ATP totalsubstrate level phosphorylation
Glycolysis: cytosol
2ATP + 2 NADH
substrate level phosphorylation
(3 per NADH) (2 per FADH2)
4 ATP
6 ATPWhy 4 or 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
NAD+
NADH + H+
e-
NADH +H+
NAD+FAD
FADH2
50:50chance
cytosol Mitoch. matrix
Pay a toll of 2 ATPs if passed to FAD
Grand Total36-38 ATPs
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Aerobic vs. Anaerobic Respiration
Aerobic requires O2:
Anaerobic does not requires O2:
Oxidative Phosphorylation
Need O2 to oxidize NADH and FADH2
(REDOX)
Fermentation: In anaerobic conditions –
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Normally:
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Fermentation: In anaerobic conditions – make NAD+creak along on 2 ATPs per glucose
1Glucose (6C)
2 Pyruvate (3C)
2 NADH + H+
2 NAD+
2ATP
O2
36-38ATPsAnaerobic no O2
Muscle Yeast, bacteria
Lactic AcidRecovery NAD+
Get by on 2 ATPs per glucose!
EthanolRecovery NAD+
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Regulation of Respiration
No O2 turn on fermentation
Feedback control
Negative allosteric regulators
Positive allosteric regulator
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