oxidative phosphorylation & electron transport chain

mitochondria

major site for aerobic respiration and the production of energy

where is the demand for energy high?

liver and muscle

cells like ______________ don't have mitochondria and rely on _______________ for energy.

erythrocytes; glycolysis

what are the structural parts of the mitochondria?

- outer membrane

- intermembrane space

- inner membrane space

- matrix

outer membrane of mitochondria

relatively permeable to small molecules and ions due to porin

- allows anionic (-) molecules to pass through

- transport occurs through porins

porin

is a voltage gated anion channel and forms pores across the membrane

inner membrane of mitochondria

impermeable to most small molecules and ions

what can pass through the inner membrane of mitochondria?

- water, gases such as CO2 and O2

- metabolites, phosphate, protons

- transport of other molecules requires specific transporters

what are the multiple folds which increase the surface area called in the inner membrane?

cristae

what does the matrix contain?

- pyruvate dehydrogenase complex

- citric acid cycle enzymes

- fatty acid b-oxidation enzymes

- amino acid oxidation enzymes

what is bound to the inner membrane?

electron transport chain

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

respiration

what are redox reactions catalyzed by?

membrane-embedded enzymes

respiratory complexes and auxiliary proteins together comprise the __________________ _____________.

respiratory chain

- aka electron transport chain

____________ _______________ - linked dehydrogenases catalyze reversible reactions between the oxidized and reduced forms of NAD(P)+

nicotinamide nucleotide

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

flavoproteins

what is another name for coenzyme Q?

ubiquinone or just q

- ubiquitous in cells

what is coenzyme Q?

a lipid-soluble benzoquinone with a long isoprenoid side chain

quinone structure

QH2 is the reduced dihydro form

what are the functions of coenzyme Q?

- a redox participant in the electron transport chain

- freely diffusible within the inner mitochondrial membrane

- plays a central role in coupling electron flow to proton movement

heme groups

tightly bound prosthetic groups

- involves fe(II) and fe(III)

cytochromes

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

what are the 3 classes in mitochondria

a, b, c

which hemes of cytochromes are not covalently bound to associated proteins?

a and b

c is covalently attached through ________ residues

cys

iron-sulfur proteins

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

what do iron sulfur proteins contain?

1, 2 or 4 Fe atoms linked sulfides

where is iron-sulfur proteins found?

membrane-bound enzymes and soluble enzymes

____________ ___________ help stabilize the enzyme structure and protect it against proteoytic attack

Fe-S clusters

how many muti-subunit enzyme complexes does the electron transport chain contain?

4

what is the name of complex I (ETC)?

NADH-Q reductase

what is the name of complex II (ETC)?

succinate-Q reductase

what is the name of complex III (ETC)?

QH2-cytochrome c reductase

what is the name of complex IV (ETC)?

cytochrome c oxidase

complex I: NADH-Q reductase

- from NADH to ubiquinone

- flavoprotein that uses FMN

- contains non-heme iron centers (Fe-S complexes)

- proton pump

in complex I (ETC) how many electron are being transferred?

2 electrons from NADH are transferred via FMN to conenzyme Q

for every 2 electrons of NADH transferred, what is being pushed out and where?

4 H+ are pushed out of the matrix into the inter-membrane space

complex II: succinate-Q reductase

- couple the oxidation of succinate with the reduction of ubiquinone

- functions to convert succinate to fumarate in the citric acid cycle

- transfers electrons but NOT a proton pump

- from succinate to ubiquinone

what does complex II contain?

- FAD

- heme molecules

- Fe-S centers

- cyt b

in complex II succinate is _______________ to fumarate.

oxidized

- FAD is reduced to FADH2

- FADH2 re-oxidized to FAD and re-enters Krebs cycle

in complex II coenzyme Q is ____________.

reduced

complex III: QH2-cytochrome c reductase

- couples the transfer of 2 electrons from ubiquinol to cytochrome c

- acts as a proton pump

- for every molecule of QH2 converted to coenzyme Q

electrons are passed one at a time from QH2 to 2 successive molecules of cyt c

what does complex III contain?

- cyt b

- cyt c

- Fe-S centers

complex IV: cytochrome c oxidase

- carries electrons from cyt c to molecular oxygen, reducing it to H2O

what does complex IV contain?

- cyt a

- cyt a3

- 2 Cu ions

what is the final electron acceptor?

O2

what is the final product?

water

electron bounce from complex 1 ,3, 4 or complex 2, 3, 4 but they do NOT bounce from complex ____ to ____.

1 to 2

in electron flow, how does energy move?

- downhill flow of electrons releases free energy

what form is energy released in?

heat and electricity

- some of the energy is used to pump protons out of the matrix

- much of the free energy generated is recovered and stored in the form of an electrochemical proton gradient across the mitochondrial inner membrane

chemiosmotic theory of oxidative phosphorylation

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

chemiosmotic theory (h's notes)

as the proton goes from high concentration to low concentration the ATP synthase absorbs some of the potential energy from the movement and uses the energy to convert ADP and inorganic phosphate to make ATP.

what does the chemiosmotic model describe?

the coupling of ATP synthesis to an electrochemical proton gradient (the proton motive force)

as the electrons flow the respiratory complex, _________ _______ ________ _________ into the inter-membrane space.

protons are pumped out

- this pumping is an "uphill" process

overtime, the protons build up outside the matrix which drive H+ back where?

into the matrix

- doing so, they transfer their energy to ATP synthase

concH+ (outside) is greater (>) than concH+ (inside): called _______________ ________________

concentration gradient

charge e- (outside) is greater (>) than charge e- (inside): called ________________ _________________

potential gradient

______ ____________ catalyzes the formation of ATP.

ATP synthase

complex V: ATP synthase

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

F1 domain is located where?

on the matrix side of the inner membrane

F0 domain is locared where?

spans the inner membrane

as H+ enters the ________ portion and turns the "stalk", ADP and Pi are joined t form ATP in the ________ domain

F0 ; F1

________ H+ enter the inter-membrane space and ______ H+ re-enters the matrix

10 ; 4

- 10/4 = 2.5 ATP per NADH (rounded to 3 ATP)

- 6/4 = 1.5 ATP per FAD2 (rounded to 2 ATP) (starts at complex II)

complexes I, III, IV are ____________ ____________.

transmembrane proteins

where is complex 2 located?

on the inner surface of the inner membrane

in complex IV, 4 H+ are ejected for every molecule of O2 that accepts the electron, what is the final acceptor?

O2

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

F0-F1 domains

What is the other name of Complex I?

a. cytochrome c oxidase

b. NADH-Q reductase

c. succinate-Q reductase

d. Q-cytochrome c reductase

e. cytochrome c reductase

b. NADH-Q reductase

What type of protein makes the outer mitochondrial membrane relatively permeable?

a. voltage gated transporter

b. proton pump

c. transporters

d. ATP-powered pump

e. porin

e. porin

What is the other name of Complex II?

a. cytochrome c oxidase

b. NADH-Q reductase

c. cytochrome c

d. Q-cytochrome c oxidoreductase

e. succinate-Q reductase

e. succinate-Q reductase

Coenzyme Q is also called:

a. Rieske center.

b. oxidoreductase.

c. ubiquinone.

d. NADH.

e. Complex II.

c. ubiquinone.

The subunit of ATPase embedded in the inner mitochondrial membrane is the:

a. membrane-c ring subunit.

b. F0 subunit.

c. anchor subunit.

d. Fm subunit.

e. F1 subunit.

b. F0 subunit.

What is the other name of Complex III?

a. NADH-Q reductase

b. Q-cytochrome c reductase

c. cytochrome c

d. cytochrome c oxidase

e. succinate-Q reductase

b. Q-cytochrome c reductase

What type of gradient is critical to ATP formation during oxidative phosphorylation?

a. potassium ion

b. proton

c. electron

d. sodium ion

e. chloride ion

b. proton

What is the other name of Complex IV?

a. NADH-Q reductase

b. Q-cytochrome c oxidoreductase

c. cytochrome c oxidase

d. cytochrome c

e. succinate-Q reductase

c. cytochrome c oxidase

An electron flow down the electron-transport chain leads to:

a. a dangerous imbalance of Na+ ions across the mitochondrial membrane.

b. the transport of protons across the inner mitochondrial membrane from the matrix to the intermembrane space.

c. the transport of protons across the inner mitochondrial membrane from the intermembrane space into the matrix.

d. a dangerous imbalance of K+ ions across the mitochondrial membrane.

e. the coupled synthesis of GTP.

b. the transport of protons across the inner mitochondrial membrane from the matrix to the intermembrane space.

What enzyme links the TCA cycle to the electron-transport chain?

a. citrate synthase

b. α-ketoglutarate dehydrogenase

c. fumarase

d. malate dehydrogenase

e. succinate dehydrogenase

e. succinate dehydrogenase

what is the name of complex III (ETC)?

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

Fe-S clusters

what do iron sulfur proteins contain?

1, 2 or 4 Fe atoms linked sulfides

what do iron sulfur proteins contain?