BCH 4033- ch.18: oxidative phosphorylation

exam 4 content

what generates most of the ATP required by aerobic cells and how?

mitochondria

using a combo of the reactions of the citric acid cycle and oxidative phosphorylation

what are mitochondria?

descendants of a free-living bacterium that established a symbiotic relationship with another cell

what happens to the synthesis of ATP in oxidative phosphorylation?

it is coupled to the flow of electrons from NADH or NADH2 to O2 by a proton gradient across the inner mitochondrial membrane

what does the electron flow through 3 transmembrane complexes result in?

the pumping of protons out of the mitochondrial matrix and the generation of a membrane potential

ATP is synthesized then the protons flow back to the matrix through ATP synthase

where are electrons from NADH first transferred to?

NADH-Q oxidoreductase (Complex I)

• first of 4 complexes with electrons emerging on QH2 (reduced form of ubiquinone (Q)

what is succinate dehydrogenase?

a component of the succinate-Q reductase complex (Complex III) that donates electrons from FADH2 to Q to form QH2

where does QH2 transfer its electrons to?

to Q-cytochrome c

• water-soluble peripheral membrane protein

where does cytochrome c transfer electrons to?

cytochome c oxidase (Complex IV)

what is the function of a heme iron ion and copper ion in the cytochrome c oxidase (Complex IV)?

transfer electrons to O2 (ultimate acceptor) to form H2O

what is the respirasome?

a large molecular structure of organized Complexes I, III, and IV

what is the result of the flow of electrons through Complexes I, III, and IV?

the transfer of protons from the matrix to the IM space

generation of a proton-motive force consisting of a pH gradient and a membrane potential

what is ATP synthesis driven by?

the flow of protons back to the matrix through ATP synthase

what is ATP synthase?

an enzyme complex that is a molecular motor made of 2 operational units

1. a rotating component

2. a stationary component

what does the rotation of ATP synthase’s gamma subunit induce?

structural changes in the beta subunit that results in the synthesis and release of ATP from the enzyme

what is the role of the glycerol phosphate shuttle?

to transfer the electrons of cytoplasmic NADH into the mitochondria so they can form FADH2 or FAD

what is the role of the malate-aspartate shuttle?

to transfer the electrons of cytoplasmic NADH into the mitochondria so they can form mitochondrial NADH

what mediates the exchange of ADP and ATP between the matrix and IM space?

2 transporters driven by membrane potential

1. ANT

2. phosphate carrier

how many molecules of ATP are generated when a molecule of glucose is completely oxidized by CO2 and H2O?

30

under what circumstances are NADH and FADH2 oxidized?

if ADP is simultaneously phosphorylated to ATP because electron transport is tightly coupled to phosphorylation

what can proteins and small molecules do that would have dramatic effects on human physiology?

inhibit oxidative phosphorylation at different points

uncouple electron transport from ATP synthesis

what does a proton gradient across the plasma membrane power?

the rotational flagellar motor of motile bacteria in a manner analogous to the way ATP synthase functions

why do proton gradients drive diverse physiological processes?

because the mechanism is fundamentally simple and can be used in many ways by proteins