Lesson 14: ETC and Oxidative Phosphorylation

Question 1

where does the source of most of the energy for ATP synthesis comes from what

Answer 1

the oxidation of NADH

Question 2

total reduced coenxymes from glycolysis and TCA:

Answer 2

glycolysis: 2 ATP and 2NADH
tca (including PDC rxns_: 8 NADH and 2 FADH2
tca: 2G(A)TP

Total: 10 NADH + 4ATP + 2 FADH2

Question 3

reduction of these coenzymes (along with the 3 ATP) yield an approximate energy return of

Answer 3

40%
- much larger energy is needed

Question 4

electron transport and ATP production occurs in the mitochondria around

Answer 4

9-11%

Question 5

ETC carries out oxidation of

Answer 5

NADH and FADH2

1 - electrons are passed through a series of. e- carrying molecules based on standard reduction potential
2 - electron carrying complexes are ordered in the inner membrane from low to high standard reduction potential

Question 6

how are the ETC components “ordered” in the IM

Answer 6

from low to high standard reductio potential

Question 7

standard reduction potentials of the major respiratory electron carriers:
NADH –> FMN

Answer 7

-69.5 kJ/mol

Question 8

FMN –> CoQ –> cytb –> cyt c1 -> cyt c –> cyt a

Answer 8

• 36.7 kJ/mol

Question 9

cyt a –> cyt a3 –> O2

Answer 9

-112 kJ/mol

Question 10

energy is released (exergonic) as electrons move from

Answer 10

reduced coenzymes through the ETC to O2 in a stepwise fashion

Question 11

where are we in the cell

Answer 11

mitochontrial matrix w/ atp synthase complexes?

• massive surface area for components of the ETC. More ATP synthase molecules = more ATP

Question 12

ATP synthesis:::::

Answer 12

1961 : Peter Mitchel postulated the “chemiosmotic theory” - the free energy of e- transport is consevrved by pumpong H+ to the IM space. The electrochemical potential of this proton gradient is harnessed to synthesize ATP

• enzyme responsibe for ATP synthesis = ATP synthase
• IM impermeable to H+ diffusion, therefore, specific proton carrier that channels H+ down concentration gradient

Question 13

F1 component of ATP Synthase

Answer 13

• catalytic component
• 3 alpha and 3 beta subunits (not the same as Hb), and 1 gamma
• the 3 beta subunits are responsible for ADP + Pi –> ATP (responsible for the synthesis, doing the actual chemistry)

Question 14

F0 component of ATP Synthase

Answer 14

• embedded in the IM
• functions in H+ transport as H+ moves down the concentration gradient; rotation of C ring (rotational energy drives)

Question 15

structure of the ATP Synthase is () conserved

Answer 15

evolutionarily
- bacterial and eukaryote yeast complex very similar

Question 16

bacterial ATP synthase complex strucutre

Answer 16

F0 = in cell membrane
F1 = in cytoplasm

Question 17

yeast ATP synthase complex structure

Answer 17

F0 = in inner mitochondrial membrane
F1 = mitochondirial matrix

Question 18

protons move through a subunit of

Answer 18

F0

Question 19

movement of H+ results in

Answer 19

rotation of C ring and gamma subunit

Question 20

rotation of gamma drives

Answer 20

conformational changes in beta subunits F1

Question 21

H+ flux translates potential energy into

Answer 21

rotational energy
- H+ binds to negatively charged Asp (alpha unit)
- protonated Asp 59 residues in C ring rotate
- H+ dissociates from Asp due to electrochemical gradient

Question 22

How is ATP synthesized: 3 phases

Answer 22

• translocation of H+
• chemistry step: formation of phosphoanhydride bond
• couple H+ gradient with ATP synthesis

Question 23

Binding change mechanism beta - subunit exists in 1 of 3 conformational states:

Answer 23

O (open) = low affinity state for substrate or product
L (loose) = ADP and P i (inorganic phosphate) binding state
T (tight) = catalytic stite ADP + Pi –> ATP

Question 24

the gamma subunit rotates in a counterclockwise direction as viewed from the matrix side

Answer 24

• as this happenes, each beta subunit is either in the O, L, or T state and it changes each time

Question 25

two famous biochemical experiments demonstrated how the rotation of the gamma induces conformational changes in the beta subunits

Answer 25

1
- actin filament is fluorescent –> attached this actin filament to the gamma subunit on the same side as the membrane
- as ATP hydrolyzed to ADP + Pi, gamma rotates counter clockwaise
- ATP “running in reverse” in vitro (ATP + H2O –> ADP + Pi)
- counterclockwise rotation can be observed with fluorescense microscopy, making ATP synthase run in reverse

Question 26

2nd experiment for conformational changes in beta subunits

Answer 26

magnetic bead can be rotated by an electromagnet
- magnetic bead is on the same side as the membrane and is attached to the streptavidin linker, attached to the gamma subunit
- gamma rotates clockwise thanks to the electromagnet (could control rotation)
- ATP synthesized in vitro (ADP + Oi –> ATP)