Chapter 19 Oxidative phosphorvlation and photophosphorylation Generation of atp by using a across membrane proton gradient, which is generated from electron flowing through a chain of carriers
Chapter 19 Oxidative phosphorylation and photophosphorylation Generation of ATP by using a acrossmembrane proton gradient, which is generated from electron flowing through a chain of carriers
ATP is synthesized using the same strategy in oxidative phosphorylation and photophosphorylation Oxidative phosphorylation is the process in which ATP is generated as a result of electron flow from nadh or Fado to o via a series of membrane bound electron carriers, called the respiratory chain (reducing O2 to H2O at the end) Photophosphorylation is the process in which AtP (and nadPh) is synthesized as a result of electron flow from H2o to NADP via a series of membrane bound electron carriers(oxidizing h,o to O, at the beginning)
1. ATP is synthesized using the same strategy in oxidative phosphorylation and photophosphorylation • Oxidative phosphorylation is the process in which ATP is generated as a result of electron flow from NADH or FADH2 to O2 via a series of membranebound electron carriers, called the respiratory chain (reducing O2 to H2O at the end). • Photophosphorylation is the process in which ATP (and NADPH) is synthesized as a result of electron flow from H2O to NADP+ via a series of membranebound electron carriers (oxidizing H2O to O2 at the beginning)
Oxidative phosphorylation and photophosphorylation are mechanistically similar Both involve the flow of electrons through a chain of membrane-bound carriers The energy released from" downhillelectron flow is first used for uphill pumping of protons to produce a proton gradient(thus a transmembrane electrochemical potential) cross a biomembrane atP is then synthesized by a downhill transmembrane flow of protons through a specific protein machinery
• Oxidative phosphorylation and photophosphorylation are mechanistically similar: – Both involve the flow of electrons through a chain of membrane-bound carriers. – The energy released from “downhill” electron flow is first used for “uphill” pumping of protons to produce a proton gradient (thus a transmembrane electrochemical potential) cross a biomembrane. – ATP is then synthesized by a “downhill” transmembrane flow of protons through a specific protein machinery
ATP synthase Outer membrane (F。F1) Freely permeable to Cristae Inner membrane Impermeable to most small molecules and ions luding H I .Respiratory electron carriers( Complexes I-IV · ADP-ATP translocases ATP synthase(FFu) her me transpo Matrix Pyruvate dehydrog Cristae(the convoluted Citric acid cycle enzymes inner membrane of Fatty acid B-oxidation mitochondria) is Amino acid oxidation where the respiratory Ribo DNA, ribosome Porin channels Many other enzymes ATP, ADP, Pi, Mg2+, Ca2,K. chain is located Many soluble metabolic intermediates
Cristae (the convoluted inner membrane of mitochondria) is where the respiratory chain is located
Intermembrane nner Transporter Citric acid cycle SCoA Co, o P+GDP GTP Pyruvate CH,-C-SCoA Acetyl CoA 3NAD 3NADH FAD FADH HSCo. ATP+ Anrt HSCOA →→FADH HSCOA NAD"NADH-FADMitochondrial Transporter matrix NADH NAD P 2e+H"+ao2→H2O NADH NAD. FAD Oxidative NAD Phosphorylation On inner menbrane of mitochondria) Electron transport complexes Transport of metabolites Pyruvate dehydrogenase and citric acid cycle into the mitochondrion ATP synthesis by FoF Fatty acid metabolism using proton-motive force Electron transport fror ATP export, ADP and P, import NADH and FADH, to oxygen; generation of proton-motive force
Oxidative Phosphorylation (0n inner membrane of mitochondria)
Photophosphorylation (on thylakoid of chloroplasts) Light Light 2H' NADP+H NADPH Stroma PSI tFd bo PSI complex Mn Plasto- cyanin 2H,.O2+ 4H 2H+ Lumen Thylakoid F membrane ADP + P ATP
Photophosphorylation (on thylakoid of chloroplasts)
2. Electrons collected in nadh and FADH are released and transported to O, via the respiratory chain The chain is located on the convoluted inner membrane(cristae) of mitochondria in eukaryotic cells(revealed by Eugene Kennedy and Albert Lehninger in 1948)or on the plasma membrane in prokaryotic cells A l. 14-volt potential difference(4E)between NADH ( 0.320 V)and O2(0.816 V)drives electron flow through the chain. D
2. Electrons collected in NADH and FADH2 are released and transported to O2 via the respiratory chain • The chain is located on the convoluted inner membrane (cristae) of mitochondria in eukaryotic cells (revealed by Eugene Kennedy and Albert Lehninger in 1948) or on the plasma membrane in prokaryotic cells. • A 1.14-volt potential difference (E`0 ) between NADH (-0.320 V) and O2 (0.816 V) drives electron flow through the chain
The respiratory chain consists of four large multi protein complexes(,Il, Ill, and Iv; three being proton pumps) and two mobile electron carriers ubiquinone(q or coenzyme Q)and cytochrome c Prosthetic groups acting in the proteins ofb l respiratory chain include flavins(fmn, fad), hemes(heme A, iron protoporphyrin IX, heme C) iron-sulfur clusters(2Fe-2S, 4Fe-4S), and copper
• The respiratory chain consists of four large multiprotein complexes (I, II, III, and IV; three being proton pumps) and two mobile electron carriers, ubiquinone (Q or coenzyme Q) and cytochrome c. • Prosthetic groups acting in the proteins of respiratory chain include flavins (FMN, FAD), hemes (heme A, iron protoporphyrin IX, heme C), iron-sulfur clusters (2Fe-2S, 4Fe-4S), and copper
NADH NAD+H NADH-CoO reductase Succinate. Co0 complex reductase complex Fumarate FMN H·out FAD FAD.+2 H CoQH2-Cytochrome c Cyt b reductase complex Hout Fe-S : 200- Four multi-protein 三兰 Complexes(LIl so IlL, and Tv) Cytochrome c oxIdase com Cyt a TTwo mobile yt a3 Electron carriers 202+2H H,O
Four multi-protein Complexes (I, II, III, and IV) Two mobile Electron carriers I II III IV
H,C HC H,C C=0 HC H CH2 H2 H-C-OH H-C-OH H-C-OH H-C-OH CH, OPO, 2 CH, OPO, CH- OPO, 2- Flavin mononucleotide Semiquinone intermediate Reduced flavin mononucleotide (FMN) (FMNH2) FMN can accept one electron (and FMNH, can donate one electron) to form a semiquinone radical intermediate
FMN can accept one electron ( and FMNH2 can donate one electron) to form a semiquinone radical intermediate