Inhibitors and Uncouplers

Inhibitors and Uncouplers Any compound that stops electron transport will stop respiration…this means you stop breathing Electron transport can be stopped by inhibiting ATP synthesis An uncoupler breaks the connection between ATP synthesis and electron transport

What is an Uncoupler? Uncouplers break the connection between electron transport and phosphorylation Electron transport is a motor Phosphorylation is the transmission Uncouplers let you put the car in NEUTRAL

O O H H O O NO2 NO2 NO2 NO2 NO2 NO2 NO2 NO2 2,4-dinitrophenol – a proton ionophore H+ H+ Inner Membrane Matrix Text p519

Thermogenin Brown Adipose Tissue Uncoupling a proton gradient from FOF1 ATPase Produces Heat!

Staying Alive Energy Wise • We need 2000 Cal/day or 8,360 kJ of energy per day • Each ATP gives 30.5 kJ/mole of energy on hydrolysis • We need 246 moles of ATP • Body has less than 0.1 moles of ATP at any one time • We need to make 245.9 moles of ATP • Each mole of glucose yields 38 ATPs or 1160 kJ • We need 7.2 moles of glucose (1.3 kg or 2.86 pounds) • Each mole of stearic acid yields 147 ATPs or 4,484 kJ • We need 1.86 moles of stearic acid (0.48 kg or 1.0 pound of fat)

Control of Oxidative phosphorylation What makes us breathe faster? How does ATP synthesis in the mitochondria adjust to the needs of the cell?

[ATP] [ADP][Pi] WHAT IS THE ATP MASS ACTION RATIO? = ATP mass action ratio High: Energy sufficient, Signifies high ATP Low: Energy debt, Signifies high ADP or low ATP HIGH Mass Action Ratio: Oxidized cytochrome C [C3+] is favored Cytochrome oxidase is low because of low C2+ O2 uptake low LOW Mass Action Ratio: Reduced cytochrome C [C2+] is favored Cytochrome oxidase stimulated because of high C2+ Oxygen uptake high

Equilibrium ½NADH + Cyt c (Fe3+) + ADP + Pi ½ NAD+ + Cyt c (Fe2+) + ATP Go’= 0 [c2+] ½ [NAD+] [c3+] [NADH] ATP [ADP][Pi] Control of Oxidative Phosphorylation Keq = [ATP] can control its own production Cytochrome c oxidase step is irreversible and is controlled by reduced cytochrome c (c2+) Because of equilibrium, concentration of c2+ depends on [NADH]/[NAD+] and [ATP]/[ADP][Pi]

ATP mass action ratio [ADP][Pi] [ATP] [c2+] ½ [NADH] [c3+] [NAD+] Control of Cytochrome Oxidase (Cox) Keq = NADH Mass Action ration equilibrium Stimulates Cox [c2+]/[c3+] NADH equilibrium Stimulates Cox ADP [c2+]/[c3+] equilibrium Stimulates Cox ATP [c2+]/[c3+] equilibrium Suppresses Cox Cytochrome oxidase controls the rate of O2 uptake which means this enzyme determines how rapidly we breathe.

Oxygen Radicals Unpairedelectron . . . . O :: O . . . . = O2- Partially reduced oxygen species Molecular Oxygen . . . . O2 O :: O . . . . O2 Octet Rule Superoxide Anion

What is aFreeRadical? Any chemical species with one of more unpaired electrons……. Highly Reactive Powerful Oxidant Short half life (nanoseconds) Can exist freely in the environment

. H . O2 . OH . NO EXAMPLES OF FREE RADICALS Hydrogen atom Superoxide (oxygen centered) Hydroxyl radical (most reactive) Nitric Oxide

PRO-OXIDANTS (Generates Free Radicals) Generates hydroxyl radical Fe2+ + H2O2 Ascorbic acid + Fe2+ Generates hydroxyl radical Paraquat Generates superoxide radical Generates superoxide radical Agent Orange Generates hydroxyl radical Ozone

WHAT ARE ANTIOXIDANTS? ENZYMES O2- Superoxide dismutase Catalase H2O2 R-OOH Peroxidases VITAMINS Vitamin E (tocopherols) Beta Carotene (pro-vitamin A) Vitamin C

Quiz 1 4 Questions 5 Points

1. Other than Fructose-6-PO4 and Fructose-1,6 bisPO4, name another phophate ester of fructose. Fructose 1-PO4 or Fructose 2,6-bisPO4 2. Other than glycerate-1,3 bisPO4, name another high energy intermediate derived from glucose in glycolysis. PEP 3. Name a compound in the Krebs cycle, which when oxidized to CO2 and H2O gives rise to 30 ATPs Succinyl-CoA 4. Name 2 pentoses that are found in the pentose phosphate pathway. Ribose-5-PO4 Ribulose-5-PO4 Xylulose-5-PO4

Inhibitors and Uncouplers