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

2022
Views:

163

Pages:

10
Author:

Jamison Bradshaw

Section 10.2: Oxidative Phosphorylation §Oxidative phosphorylation – energy generated by ETC conserved by phosphorylation of ADP to ATP §Chemiosmotic coupling theory §Energy released by ETC creates electrochemical gradient §Gradient drives ATP synthesis Figure 10.11 Overview of the Chemiosmotic Model Section 10.2: Oxidative Phosphorylation §Chemiosmotic Theory 1. Electrons pass through ETC § § Protons pumped into intermembrane space, Generates proton motive force 2. Protons move back across membrane via ATP synthase driving ATP formation § Thermodynamic favorable flow of protons Figure 10.11 Overview of the Chemiosmotic Model Section 10.2: Oxidative Phosphorylation Figure 10.12 Uncouplers Evidence for chemiosmotic theory: 1. pH drops in a weakly buffered mitochondria suspension when actively respiring 2. Disruption of inner membrane stops respiration 3. Uncouplers and ionophores (e.g., gramicidin A) disrupt the proton gradient, inhibiting ATP synthesis Section 10.2: ATP Synthesis ATP synthase – ‘lollipop’-shaped structure; 2 components §F1 unit – active ATPase §5 different subunits §3 nucleotide binding catalytic sites §Requires translocation of three protons §F0 unit -transmembrane channel §3 different subunits §Inhibited by oligomycin Figure 10.13 The ATP Synthase Section 10.2: ATP Synthesis §Consists of two rotors linked by a strong flexible stator §F0 motor converts the proton motive force into rotational force that drives ATP synthesis §C ring – revolving component, §e/g subunit – central shaft §Rotates within a,b hexamer of F1 unit §Stator – b/d subunit; prevent rotation Figure 10.14 The ATP Synthase From Escherichia coli Section 10.2: ATP Synthesis §b subunits of the ATP synthase have three conformations: open (O), tight (T), and loose (L) §Steps: 1. ADP and Pi bind to L site; rotation converts it to T conformation 2. ATP synthesized 3. Rotation converts T site to O site, releasing ATP Figure 10.15 ATP Synthesis Model Section 10.2: Control Oxidative Phosphorylation §Respiratory control - activates when ADP and Pi concentrations high §Inhibited when ATP concentrations high §ADP-ATP translocator controls amounts of ATP & ADP in mitochondria §Phosphate carrier (H2PO4-/H+ symporter) – controls amount of H2PO4-/H+ Figure 10.16 The ADP-ATP Translocator and the Phosphate Translocase Section 10.2: Oxidative Phosphorylation Figure 10.17a Shuttle Mechanisms That Transfer Electrons from Cytoplasmic NADH to the Respiratory Chain §Glycerol phosphate shuttle §cytoplasmic NADH reduces DHAP into glycerol-3phosphate § glycerol-3-phosphate oxides FAD à FADH2 §Produces 1.5 ATP Section 10.2: Oxidative Phosphorylation Malate-aspartate shuttle § Cytoplasmic NADH reduces oxaloacetate to malate § Transported to matrix § Malate is reoxidized to produce NADH § OAA returned to cytroplasm via transamination reaction converting it to aspartate § Produces 2.25 ATP Figure 10.17b Shuttle Mechanisms That Transfer Electrons from Cytoplasmic NADH to the Respiratory Chain Section 10.2: Oxidative Phosphorylation