Inhibitors and Uncouplers
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Transcript of Inhibitors and Uncouplers
Inhibitors and Uncouplers
Table 1. Inhibitors of Respiration and Oxidative Phosphorylation
Site-Specific Target Complex
Carbon monoxide IVCyanide IVSodium Azide IVRotenone IAntimycin A IIIAmytal I
Phosphorylation
Oligomycin Fo
Uncouplers
2,4-Dinitrophenol (DNP) Proton gradientTrifluorocarbonylcyanide Phenylhydrazone (FCCP) Proton gradient
Any compound that stops electron
transport will stop respiration…this means you stop
breathing
Any compound that stops electron
transport will stop respiration…this means you stop
breathing
Electron transport can be stopped by
inhibiting ATP synthesis
Electron transport can be stopped by
inhibiting ATP synthesis
An uncoupler breaks the connection between
ATP synthesis and electron transport
An uncoupler breaks the connection between
ATP synthesis and electron transport
What is an Uncoupler?
Uncouplers break theconnection betweenelectron transport andphosphorylation
Electron transport is a motor
Phosphorylation is the transmission
Uncouplers let you put the car in NEUTRAL
Table 2. Action of Inhibitors on Respiration and Phosphorylation
Agent or Condition O2 uptake ATP synthesis
1. Inhibit electron transport……….
2. Inhibit phosphorylation………..
3. Increase proton gradient……….
4. Decrease proton gradient………
5. Add DNP………………………
6. Add Oligomycin……………….
7. Add Oligomycin + DNP………
O
NO2
NO2
2,4-dinitrophenol – a proton ionophore
H+
O
NO2
NO2
H O
NO2
NO2
H O
NO2
NO2
H+
Inner MembraneMatrix
Text p519Text p519
Brown Adipose Tissue
Uncouplinga proton gradientfrom FOF1 ATPaseProduces Heat! Thermogenin
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)
Controlof
Oxidative phosphorylation
What makes us breathe faster?
How does ATP synthesis in the mitochondria adjust to the needs of the cell?
[ATP][ADP][Pi] = ATP mass action ratio
Low: Energy debt, Signifies high ADP or low ATP
High: Energy sufficient, Signifies high ATP
HIGH Mass Action Ratio:
WHAT IS THE ATP MASS ACTION RATIO?
Oxidized cytochrome C [C3+] is favored
Cytochrome oxidase is low because of low C2+
O2 uptake lowLOW Mass Action Ratio:
Reduced cytochrome C [C2+] is favored
Cytochrome oxidase stimulated because of high C2+
Oxygen uptake high
ATP[ADP][Pi]
[NAD+][NADH]
½Keq =
[c2+][c3+]
½NADH + Cyt c (Fe3+) + ADP + Pi ½ NAD+ + Cyt c (Fe2+) + ATP Go’= 0
Control of Oxidative PhosphorylationControl of Oxidative Phosphorylation
EquilibriumEquilibrium
[ATP] can control its own production
Cytochrome c oxidase step is irreversible and is controlled byreduced cytochrome c (c2+)
Because of equilibrium, concentration of c2+ depends on [NADH]/[NAD+] and [ATP]/[ADP][Pi]
[c2+][c3+]
[NADH] [NAD+]
½ [ADP][Pi] [ATP]= Keq
NADH
ATP mass action ratioATP mass action ratio
Mass Action ration
NADH [c2+]/[c3+]
equilibrium
equilibrium
ADP [c2+]/[c3+]
ATP [c2+]/[c3+]
equilibrium
equilibrium
Cytochrome oxidase controls the rate of O2 uptake whichmeans this enzyme determines how rapidly we breathe.
Cytochrome oxidase controls the rate of O2 uptake whichmeans this enzyme determines how rapidly we breathe.
Control of Cytochrome Oxidase (Cox)
Stimulates Cox
Stimulates Cox
Stimulates Cox
Suppresses Cox
O2
O2 O :: O..
. ....
.Octet Rule
...
..O :: O. ..
Molecular Oxygen
= O2-
Unpaired electronUnpaired electron
Oxygen Radicals
Superoxide Anion
Partially reduced oxygen species
What is a Free Radical ?
Highly Reactive
Powerful Oxidant
Any chemical species with one of more unpairedelectrons…….
Short half life (nanoseconds)
Can exist freely in the environment
EXAMPLES OF FREE RADICALS
H. Hydrogen atom
O2 . Superoxide (oxygen centered)
.OH Hydroxyl radical (most reactive)
.NO Nitric Oxide
PRO-OXIDANTS (Generates Free Radicals)
Fe2+ + H2O2
Ascorbic acid + Fe2+
Paraquat
Agent Orange
Ozone
Generates hydroxyl radical
Generates hydroxyl radical
Generates hydroxyl radical
Generates superoxide radical
Generates superoxide radical
WHAT ARE ANTIOXIDANTS?WHAT ARE ANTIOXIDANTS?
ENZYMES
VITAMINS
Superoxide dismutase
Catalase
Peroxidases
O2-
H2O2
R-OOH
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.
2. Other than glycerate-1,3 bisPO4, name another high energy intermediate derived from glucose in glycolysis.
3. Name a compound in the Krebs cycle, which when oxidized to CO2 and H2O gives rise to 30 ATPs
4. Name 2 pentoses that are found in the pentose phosphate pathway.
Fructose 1-PO4 or Fructose 2,6-bisPO4
PEP
Succinyl-CoA
Ribose-5-PO4 Ribulose-5-PO4 Xylulose-5-PO4