University:
Glendale Community College
Course:
BIO160 | Introduction to Human Anatomy and Physiology
Academic year:

2022
Views:

312

Pages:

12
Author:

arborezmv

Section 10.1: Electron Transport Series of electron carriers in order of increasing electron affinity §Inner mitochondrial membrane NADH/FADH2 -> Co-Q -> cytochromes -> O2 § Glucose à CO2 + water §Aerobic respiration couples electron transfer ultimately to ATP synthesis §Protons pumped (H+) creates pH gradient §Drives synthesis of ATP Figure 10.1 The Electron Transport Chain §Chemiosmotic coupling – results from stored potential energy, basis for coupling between oxidation & phosphorylation Section 10.1: Electron Transport §NADH à E-FMN §E-FMN à Fe clusters §Fe clusters à Co-enzyme Q Complex I §Co-enzyme Q à Cytochrome b (Q cycle) §Cytochrome b à Fe clusters §Fe clusters à Cytochrome C §Cytochrome C à Cytochrome A §Cytochrome A à oxygen Complex III Complex IV Section 10.1: Electron Transport §Complex I - transfer of electrons from NADH to ubiquinone (CoQ) CoQH2 §NADH dehydrogenase complex §Large complex - >20 subunits §1 molecule FMN, 7 Fe clusters §Flavin mononucleotide (FMN) oxides NADH à FMNH2 NADH + H+ E-FMN àNAD+ + E-FMNH2 à Feox à Fered à CoQ à CoQH2 Figure 10.2 Two Iron-Sulfur Clusters Section 10.1: Electron Transport §Electrons transfer: NADH to FMN àFMNH2 §FMNH2 à iron sulfur centers §Iron/sulfur centers à CoQ §Movement of protons from matrix to intermembrane space Figure 10.4 Electron Movement through Complex I of the Electron Transport Chain Section 10.1: Electron Transport - transfers electrons from succinate from CAC to UQ §Succinate dehydrogenase complex §Four subunits (ShdA-D) – ShdA - succinate binding site; ShdB - 3 iron-sulfur clusters; ShdC & D integral membrane proteins §Located in inner mitochondrial membrane §Does not translocate protons Figure 10.5 Path of Electrons from Succinate, Glycerol-3-Phosphate, and Fatty Acids to UQ Section 10.1: Electron Transport - electrons from reduced UQ (UQH2) to cytochrome c Cytochrome bc1 complex §Cytochromes - proteins with heme prosthetic group §cyt b, cyt c, several iron/sulfur proteins §Electrons change oxidation state of heme iron (reduced Fe2+ to oxidized Fe3+) Figure 10.6 Structure of Cytochrome c Section 10.1: Electron Transport Figure 10.7 Electron Transport through Complex III - transfer of electrons through complex III §Cytochrome c is a water-soluble mobile electron carrier on outer face of the inner membrane §Two molecules of cyt c per one molecule of CoQ §Cyt c carries e-, H+ leaves matrix CoQH2 = 2cyt cox (Fe+3) = 2H+matrix à CoQ + 2cyt cred(Fe+2) + 4H+cytosol Section 10.1: Electron Transport - four electron reduction of O2 to H2O §cytochrome oxidase §Contains cytochrome a, a3, 3 copper ions §CuA-CuA accepts electrons, passes to cyt a, àcyt a3 à CuB § Four electrons & four protons are passed to O2 to form H2O 2Cyt c[Fe(II)] + 2H+ + 1/2O2 ---> 2 Cyt c[Fe(III)] + H2O §ATP - allosteric inhibitor of cytochrome oxidase §Binds to complex IV and cyt c Section 10.1: Electron Transport Section 10.1: Electron Transport Figure 10.9 Energy Relationships in the Electron Transport Chain §NADH oxidation -substantial energy release §Used to pump protons into intermembrane space §Establishes a proton gradient §2.5 molecules ATP per NADH §1.5 molecules ATP per FADH2 Section 10.1: Electron Transport Inhibitors Figure 10.10 Inhibitors of the Electron Transport Chain §When electron transport is inhibited, O2 consumption is reduced or eliminated §Antimycin A inhibits cyt b in Complex III §Rotenone & amytal inhibit NADH dehydrogenase in Complex I §Cytochrome oxidase – inhibited by CO, azide (N3-), cyanide (CN-) Section 10.1: Electron Transport 4H+ 4H+ 4H+ 4H+