Electron Transport ChainElectron Transport Chain

ReviewReviewGlycolysis & the Krebs Cycle only

produce 4 ATP/glucoseMost of the energy from glucose

is stored in NADH or FADH2

LocationLocationThe Electron

Transport Chain (ETC) takes place along the Inner Mitochondrial Membrane

ComponentsComponentsMost components

of the Electron Transport Chain are protein complexes

These complexes have Prosthetic Groups◦ Essential non-

protein components

The entire Electron Transport Chain consists of 4 transmembrane structures as well as a pair of electron carriers

Most structures are made up of more than one protein

NADH Dehydrogenase NADH Dehydrogenase (Complex I)(Complex I)NADH is oxidized and in turn

reduces flavin mononucleotide (FMN)

FMN participates in another redox reaction with an Iron-Sulfur protein◦FMN is oxidized, Fe•S is reduced

First Electron CarrierFirst Electron CarrierFe•S part of NADH

Dehydrogenase pass the electrons to Ubiquinone (Q)◦Lipid electron carrier◦Transports the electrons to

Cytochrome b-c1 complex

Cytochrome Cytochrome bb--cc11 Complex Complex (Complex III)(Complex III)Cytochrome b (Cyt b) accepts the

electrons from Q Electrons are passes from Cyt b

to another iron-sulfur protien before being passed to Cytochrome c1

Second Electron CarrierSecond Electron CarrierCytochrome c1 passes the

electrons to the second electron carrier, Cytochrome c

Cytochrome c operates on the outside of the inner mitochondrial membrane (in the intermebrane space)

Cytochrome Oxidase Cytochrome Oxidase Complex (Complex IV)Complex (Complex IV)Consists of two protein complexes:

Cytochrome a and Cytochrome a3

Cytochrome a receives the electrons from Cytochrome c and then transfers electrons to Cytochrome a3

Cytochrome a3 passes the electrons onto Oxygen◦Combines with hydrogen atoms in the

Matrix to form water

Each transfer of electrons is an exothermic redox reaction◦The energy is used to transfer a

single H+ ion into the Intermembrane Space

Oxygen (due to its high electronegativity) is the only element available to accept electrons at the end

FADH2 transfers its electrons to a lower energy level than NADH Electrons join up with

Ubiquinone (Q) hence

NADH 3 H+ moved

FADH2 2 H+ moved

FADH2

FAD

ChemiosmosisChemiosmosisThe final stage of Oxidative

PhosphorylationThe complexes of the ETC create

a electrochemical gradient of H+ across the inner membrane◦H+ want to return to equilibrium

ATP SynthaseATP SynthaseProtein imbedded

in the inner mitochrondia membrane

Allows H+ ions back through into the matrix

Uses this Proton-Motive Force to convert ADP and ATP◦ Each H+ ion let back

into the matrix creates 1 ATP

Energy Tally/Glucose Energy Tally/Glucose MoleculeMoleculeGlycolysis 2 ATPKrebs Cycle 2 ATPETC

NADH (Glycolysis) 4-6 ATPNADH (Prep Step) 6 ATPNADH (Krebs) 18 ATPFADH2 4 ATP

36-38 ATP