05: Oxidative Phosphorylation and Electron Transport Chain Notes

what are the structural parts of mitochondria

Outer membrane, Intermembrane space, Inner membrane, Matrix

Structure of Mitochondrial Membranes: outer membrane

• Relatively permeable to small molecules and ions due to _______

  • allows _____ molecules to pass through

porin, anionic

Structure of Mitochondrial Membranes: inner membrane

• impermeable to most small molecules and ions

• Multiple folds to increase the surface area called ______

cristae

_____ is the most important part of mitochondria

• Contains major and important metabolic enzymes

• Enzymes for TCA cycle, fatty acid oxidation

Matrix

Electron Transport Chain (ETC) is bound to the _____

• Matrix also contains genetic material

• Needed to synthesize key mitochondrial proteins, including enzymes

inner

NADH and FADH2 transfer their electrons to molecular O2 through a series of redox reactions in a process called _______

• Molecular oxygen is vital to the process

respiration

___________ catalyze reversible reactions between the oxidized and reduced forms of NAD(P)+

• Two hydrogen atoms are removed from the substrates:

  • One is transferred as a hydride ion (:H-) to NAD(P)+

  • One is released as H+

Nicotinamide nucleotide-linked dehydrogenases

______ = contain a very tightly, sometimes covalently, bound flavin nucleotide (FMN or FAD)

• The oxidized flavin nucleotide can accept either:

  • One electron (yielding the semiquinone form) or

  • Two electrons (yielding FADH2 or FMNH2)

Flavoproteins

________ is a redox participant in the electron transport chain

• a lipid-soluble benzoquinone with a long isoprenoid side chain

• Freely diffusible within the inner mitochondrial membrane

• Plays a central role in coupling electron flow to proton movement

Coenzyme Q, Ubiquinone, Q

Tightly bound prosthetic groups

• Participate in electron transfer

• Involves Fe(II) and Fe (III)

Heme Groups

_______ = proteins with characteristic strong absorption of visible light due to their iron-containing heme prosthetic groups

• heme a and b are not covalently bound

• heme c covalently attached through Cys residues

Cytochromes

• ________ = proteins that contain iron in association with inorganic sulfur atoms and/or with the sulfur atoms of Cys residues in the protein

  • participate in one-electron transfers

  • Non-heme iron complexes

iron-sulfur protein

____________ help stabilize the enzyme structure and protect it against proteolytic attack

Fe-S clusters

Complex I

NADH-Q reductase, NADH to ubiquinone

Complex II

Succinate-Q reductase, succinate to ubiquinone

Complex III

QH2-cytochrome c reductase, ubiquinone to cytochrome c

Complex IV

Cytochrome c oxidase, cytochrome c to O2

Complex I: NADH-Q reductase is a Flavoprotein that uses _____, contains non-heme iron centers(________), where electrons from NADH are transferred via FMN to coenzyme Q

FMN, Fe-S complexes

Complex II: Succinate-Q reductase couples the oxidation of succinate with the reduction of ubiquinone

• also functions to convert succinate to fumarate in the citric acid cycle

• Transfers electrons

• Does not act as a proton pump

• Contains FAD, heme molecules, Fe-S centers, and cyt b

Succinate is _______ to fumarate, while Coenzyme Q is _______

oxidized, reduced

Complex III: QH2-cytochrome c reductase couples the transfer of 2 electrons from _______

• Contains cyt b, cyt c and Fe-Scenter

• Acts as a proton pump

• For every molecule of QH2 converted to Coenzyme Q, 4 H+ are pushed out of the matrix into the intermembrane space

ubiquinol to cytochrome c

Complex IV: Cytochrome c oxidase contains cyt a, cyt a3 and two Cu ions

• Carries electrons from cyt c to molecular oxygen, reducing it to H2O

• ______is the final electron acceptor

• ______ is the final product

O2, Water

_________ = transmembrane differences in proton concentration are the reservoir for the energy extracted from biological oxidation reactions

chemiosmotic theory

Proton Motive Force

• As the electrons flow through the respiratory complex, protons are pumped out into the inter-membrane space → This pumping is an “uphill” process

  • ConcH+ (outside) >> ConcH+ (inside) concentration gradient 

  • Chargee- (outside) >> Chargee- (inside) : potential gradient

• This drives the H+ back into the matrix → In doing so, they transfer their energy to ATP synthase

• ______- catalyzes the formation of ATP

ATP synthase

Complex V: _______

• drives the synthesis of ATP from ADP and Pi, as protons flow passively back into the matrix through its proton pore

ATP synthase

Complex V

• F1 domain is located on the ______ of the inner membrane

• F0 domain spans the _______

• As H+ enters the F0 portion and turns the “stalk”, ADP and Pi are “joined” to form ATP in the F1 domain

matrix side, inner membrane

_________ is the movement of ions across a semipermeable membrane bound structure, down their electrochemical gradient

Chemiosmosis

_________ = transmembrane differences in proton concentration are the reservoir for the energy extracted from biological oxidation reactions

chemiosmotic theory

Chemiosmotic model

• ______ H+ enter the inter-membrane space, and _______ H+ re-enters the matrix

10, 4

______ ATP per NADH

3

_______ per FAD

2

Complexes________ are transmembrane proteins

I, III, IV

Complex II is on the _____ of the inner membrane

inner surface

_________ is not a proton pump

Complex II

In complex IV, 4 H+ are ejected for every molecule of O2 that accepts the e- (______ is the final acceptor)

O2

Complex V or ________ is a distinct protein complex

• It is not a part of the other four complexes

ATP synthase

ATP synthesis by the ________ of ATP synthase is accompanied by H+ re-entry into the matrix

F0-F1 domainscomplex

3 H+ re-enter from ATP synthase, and one H+ is imported along with inorganic phosphate

• Net 4 H+ re-enter

• ATP from NADH = _________ = 2.5 ATP (rounded to 3 ATP)

• ATP from FADH2 = _______= 1.5 ATP (rounded to 2 ATP)

10/4, 6/4