Chapter 18Chapter 18

Electron Transport and Oxidative PhosphorylationOxidative Phosphorylation

Overview of electron transport

I t bIntermembranespace

Inner

Outermembrane

Redox Potentials

The bigger the numberThe greater the electron affinity

The electron transportChain is UNI-directionalSystem based uponINCREASING REDOX POTENTIALS

The Final acceptor is Oxygen!

Mobile electronCarriers, carry electronsBetween the stationary carriers

Electrons Flow!!!

http://vcell.ndsu.nodak.edu/animations/etc/movie.htm

Cytochrome C is a conserved Molecule

It l t h ttl l t b t t ti lIts role to shuttle electrons between stationary complexesHas NOT changed for billions of years!!!

ComparingCytochrome Cy

Genes to formA phylogeneticTreeTree

The more similarThe amino acidSequence if of cytochrome C, The more closely related theSpecies areSpecies are.

The Hazards of the electron transport chain. An oxygen that is not completelyReduced to water will form free radicals.

Superoxide Dismutase (SOD) enzyme helps to clear theFree radicals.

The generation of a proton gradient – the theory

The proton gradient powers ATP production

A Test of the theory in An artificial system (mitochondria)

ATP Synthase is an elaborateMolecular Energy converter!

1 Converts potential energy of1. Converts potential energy ofa proton gradient into kinetic energyOf rotation!

2. Rotational kinetic energy it convertedinto chemical potential energy in an ATPMolecule!

The process is called oxidativePhosphorylation! It makesPhosphorylation! It makesATP more efficiently thanSubstrate level phosphorylation!Substrate level phosphorylation!

Detecting rotation –

Fixed the bottom of ATP synthaseOn a glass slide, and tetheredA fluorescent actin filamentH dl h iHandle on to the rotatingGama (g) subunit

Added ATP and observed…Added ATP and observed…

http://www.res.titech.ac.jp/~seibutu/hisabori/fig2.mov

http://vcell.ndsu.nodak.edu/animations/atpgradient/movie.htm

Translocase antiporter in the mito innermembrane helpMove ATP out and ADP in the matrixMove ATP out and ADP in the matrix

~30 ATPsPer glucose

Opening the p gFlood Gates!

Releasing the gStored Energy

Randomly!Randomly!

Opening the “Flood Gates”!

Releasing the Stored EnergyFlood Gates ! Stored Energy

Randomly!

Skunk cabbage UCP-1 Uncouples the gradient = thermogenesisSkunk cabbageHibernationInfant mammals “nonshiver” heat generation

Inhibitors of the electronT t h iTransport chain

Good or Bad for ATP production?

A chemical “uncoupler” of the proton gradient