Cellular CatabolismThe Electron Transport Chain & Oxidative Phosphorylation Packet #28 Chapter #9
Summary Thus Far… • At the end of the Krebs Cycle, and before the cell makes more ATP at the electron transport chain, produced so far is… • 2 NET ATP • Glycolysis • 2 GTP • Kreb’s Cycle • Later changed to ATP • 2 FADH • Kreb’s Cycle • 10 NADH • 2 from Glycolysis • See upcoming slides. • 2 as pyruvate is changed to ACoA • 6 from the Kreb’s Cycle • 6 CO2 • 4 from the Kreb’s Cycle • 2 as pyruvate is changed to ACoA
Oxidative Phosphorylation vs. Chemiosmosis • Oxidative Phosphorylation • Process in mitochondria in which ATP formation is driven by the transfer of electrons from food molecules to oxygen. • The ultimate destination of the electrons, that originated with the food molecule (glucose), is oxygen. • This oxygen atom is combined with H+ ions to make H2O. • More to come later
Oxidative Phosphorylation vs. Chemiosmosis II • Chemiosmosis • Also known as chemiosmotic coupling • This is the mechanism in which a gradient of hydrogen ions (a pH gradient), across the inner mitochondria membrane, is used to drive an energy requiring process. • Examples • ATP production at the electron transport chain • The transport of a molecule across a membrane. • Flashback to previous packet. • Co-transport
Oxidative Phosphorylation vs. Chemiosmosis III • What is the connection between Oxidative Phosphorylation and Chemiosmosis? • In order for oxidative phosphorylation to occur, chemiosmosisMUST be part of the process.
Goal of the Electron Transport Chain I • The function of the electron transport chain is to convert all of the previously made NADH and FADH into ATP. • This happens via oxidative phosphorylation. • The electron transport chain is located in the inner membrane of the mitochondria and is composed of 5 complexes • Electron carriers and ATP synthase. • The complexes, of the electron transport chain, are used to produce large amounts of ATP
Yields of ATP • 1 FADH produces 2 ATP’s • 1 NADH produces 3 ATP’s • However, one must be mindful of what happens to the NADH entering into the mitochondria after glycolysis has occurred.
NADH, Glycolysis & The Electron Transport Chain • Remember that glycolysis occurs in the cytosol of the cell. • The NADH produced is in the cytosol of the cell. • The NADH produced in the cytosol of the cell must enter the mitochondria via shuttles.
NADH, Glycolysis & The Electron Transport Chain II • There are TWO types of shuttles used for moving the NADH produced in the cytosol into the mitochondria matrix. • Glycerophosphate shuttle • Changes NADH into FADH as it transported into the mitochondria • Malate-aspartate shuttle • NADH remains as NADH as it transported into the mitochondria
ATP Synthase • As the hydrogen ions, resulting from the change of NADH to NAD+, are pumped across ATP synthase (Complex #5), ADP & P are changed into ATP.
Calculating the Total Amount of ATP’s per Glucose Molecule • Glycolysis • 2 net ATP • substrate level phosphorylation—chemical reactions • 4-6 ATP (2 NADH) (Shuttles) • Pyruvate to ACOA • 6 ATP (2 NADH) • Krebs Cycle • 2 ATP • From 2 GTP’s • 18 ATP (6 NADH) • 4 ATP (2 FADH) • In the end we have a total of 36-38 net ATPs generated.
Drugs That Impact the Production of ATP at the Electron Transport Chain • Oligomycin • Drug that binds to the stalk of ATP synthase and closes the H channel • 2, 4-dinitrophenol • This is an uncoupler • These increase the permeability of the inner mitochondrial membrane to protons • Causes electron transport to proceed at a rapid rate without the establishment of a gradient • The energy produced by the transport of electrons is released as heat rather than being used to synthesize ATP • Fever • Aspirin is an uncoupler • This is what explains fevers with overdoses
Regulation of Glycolysis/Cell Respiration • Regulation is via allosteric activation or inhibition or via the phosphorylation or dephosphorylation of rate-limiting enzymes. • Phosphofructokinase is inhibited by ATP and activated by AMP • Enzyme used to make fructose 1, 6 bisphosphate • Inhibition by citrate • First intermediate of the Kreb’s Cycle