Molecular Cell Biology Fifth Edition Chapter 8: Cellular Energetics Copyright © 2004 by W. H....
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Transcript of Molecular Cell Biology Fifth Edition Chapter 8: Cellular Energetics Copyright © 2004 by W. H....
Molecular Cell BiologyFifth Edition
Chapter 8:Cellular Energetics
Copyright © 2004 by W. H. Freeman & Company
Harvey Lodish • Arnold Berk • Paul Matsudaira • Chris A. Kaiser • Monty Krieger • Matthew P. Scott •
Lawrence Zipursky • James Darnell
How cell generate ATP?
ATP :
1. synthesis of protein and nucleic acid
2. transport molecules against concentration gradient
3. movement of cilia
Chemiosmosis
ATP generation for bacteria, mitochondria, and
chloroplast
Occur only in sealed membrane
Stepwise movement of electrons for higher energy
state to low energy state through electron carrier
Proton motive force:
Supply energy for transporting small molecule across membrane and against its concentration gradient
ATP synthase
Endocytosis of bacteria by eukaryotic cells forms mitochondria and chloroplast
Bact plasma membrane=
matrix phase of inner
mitochondrial membrane=
stroma face of thylakoid
membrane
Oxidation of glucose and fatty acid to CO2
ATP formed by substrate level phosphorylation
No-proton motive force involved
Transfer of 4 H+ and 4 e to NAD+
Aerobic oxidation of fatty acid and pyruvate in mitochondria
Oxidation of pyruvate and fatty acid to CO2 and
coupled reduction of NAD+ to NADH and FADH2
Electron transfer from NADH and FADH2 to O2
Harness energy stored in electrochemical gradient
for ATP synthesis by F0F1 complex
TCA cycle
Oxidation of of acetyl coA
No O2 involved in the oxidation
energy stored in the reduced form of NADH and FADH2
Mitochondria membrane is impermeable to NADH
How does NADH enter mitochondria ?
----- malate aspartate shuttle
1. malate/-ketoglutarate antiport
2. glutamate/aspartate antiport
NADH cytosol + NAD+ NAD+ cytosol+ NADHmatrix
Peroxisome
single membrane
oxidize long chain fatty acid
generate no ATP
electron from FADH2 produced during
oxidation of FA was transferred O2 and generate H2O2\
NADH is exporeted to cytosol and reoxidize
No citric acid cycle---acetyl coA genetated was send to
cytosol for cholesterol synthesis
Allosteric control of glucose metabolism
1. Hexoinase: inhibited by glucose 6-phosphate
2. Pyruvate kinase: inhibited by ATP
3. Phosphofructokinase :
rate limiting enzyme of glycolic pathway
inhibited by ATP and citrate
stimulated by insulin
activated by fructose 2.6. biphosphate( feed
forward control)
NADH+H++1/2O2 NAD++H2O G=-52.6Kcal/mol
FADH2+H++1/2O2 NAD++H2O G=-43.4Kcal/mol
Total G for 1 glucose molecule CO2 = -613kcal/mol
( 10 NADH +2 FADH2)
Release of respiratory free energy from electron transfer and transfer of energy in proton motive force
Higher redox potential
Different prothetic group
Lower redox potential
Electron flow orders:
b→c1 →c →a →a3
heme, iron containning prothetic group
Iron sulfur cluster, non-heme , iron containning prothetic group
Electron transfer from NADH or FADH2 to O2 is coupled to pronton transport across the mitochondria membrane
Releasing of protons to the solution
CoQ and Three electron transport complex pump protons out of mitochondria matrix
Isolation of individual complex
↓pack by liposome
↓add e- donor and
acceptor
↓ monitoring pH
change
Q cycle: 2 protons/one e- transfer
Binding of CoQ to Qo site
↓ CoQ H2 bind to Qi
↓ releasing of 2H+ to
intermembrane space
Binding of CoQ to Qo site
↓ CoQ H2 bind to Qi
↓ releasing of 2H+ to intermembrane space
Q cycle: 2 protons/one e- transfer
Model of the structure and function of ATP synthase in the FoF1 complex) in the bacterial plasma membrane
hexamer
F0
a1b2c10
Common in bacterial and yeast
12C subunit in donut shape
F1
water soluble
33
Required for ATP synthesis but not for electron transport
The binding change mechanism of ATP synthesis from ADP and Pi by the F0 F1 complex
O: bind ATP poorly, and ADP+Pi weakly
L: bind ADP+Pi more strongly
T: bind ADP+Pi tightly
The phosphate and ATP/ADP transport system in the inner mitochondrial membrane
Powered by pronton motive force for the exchange of ATP formed and ADP+pi
Respiratory control
Rate of Motochondria oxidation normally depends on ATP
level
Oxidation of FADH2 and NADH occur ed only there is a source
of ADP and Pi
Coupling of NADH and FADH2 oxidation and proton transport
across inner mitochondrial membrane and ATP synthesis is
important in maintaining the membrane electro potential
DNP: uncoupler of mitochondria membrane potential
shuttle proton from intermembrane space to matrix and
abolish ATP synthesis
Thermogenin
A natural uncoupler in brown fat mitochondrial membrane
Oxidize NADH and convert the energy to heat
Slow in proton transport
a.a. sequence similar to ATP/ADP anti-port
Four stages in photosynthesis
1. Absorption of light
light absorpthin by chlorophyll on thylakoid membrane
2 H2O → O2 + 4H++ 4e- transfer of e- to quinone Q
2. Electron transport and generation of a proton motive force
2 H2O+ 2NADP+ light 2H+ + 2NADPH + O2
3. Synthesis of ATP
4. Carbon fixation
synthesis of polymer of 6-C sugars from CO2 and H2O
Phtosystem
1. Light reaction center
chlorophyll a : function both as light reaction and harvesting
chlorophyll b : seen in vascular plant
carotenoid : seen in plant and bacteria
2. Light harvesting complex( LHCs)
Light harvesting complex( LHCs)
Initiate photoelectric transport
Genomic arrangement for maximun light absorbance
Linear electron flow in plants, requires both chliroplast photosystems PSI and PSII
→Combination of different absorbance of light source enhances the rate
of photosynthesis
Splitting of H2O due to lower
reduction energy than p680, replenish
electron in p680
No splitting of H2O
Unbalance excitation of two photosystem
Dissociation of PSII from LHCII
Support cyclic electron flow and ATP synthesis
Light and Rubisco activase stimulate CO2 fixation
Thioredoxin in Dark Reduced thioredoxin activate calvin cycle enzymes
Leaf anatomy of C4 plant
Assimilate CO2 into 4C molecules at low ambient CO2 and deliver to the interior bundle sheath