What is name of Coenzyme Q?
Ubiquinone
The ______is a supramolecular complex involving complexes I, II, and III.
Respirasome
ATP synthesis is coupled to electron transport via a ________ across the mitochondrial membrane.
Proton gradient
Examples of inhibitors of ATP synthase
Oligomycin, dicyclohexylcarbodiimide
Example inhibitors of Complex I
- Rotenone
- Amytal
_______cycle shuts down if no ATP synthesis occurs
TCA
Where do the electrons donated to Coenzyme Q go?
Complex III (Q- Cytochrome C Oxidoreductase)
Example inhibitors of Complex IV
CN-, N3- (azide), CO
Example of an uncoupling protein
UCP-1 (thermogenin)
Final electron acceptor
O2
There are no direct transporters for ____, ____, and ______.
NADH, acetyl CoA, and Oxaloacetate
Example inhibitors of Complex III
Antimycin A
Malate-aspartate shuttle
- Donates electrons from NADH to Complex I
- Involves the transport of malate/a-ketoglutarate and aspartate/glutamate
Complex IV
- Cytochrome c oxidase
- Pumps 2 protons
Complex III
- Q-cytochrome c oxidoreductase
- Receives electrons from Co enzyme Q
- Pumps 4 protons
- Donate electrons to Cytochrome C
Glycerol-3-phosphate shuttle
- Shuttles electrons from FADH2
- Donates electrons to Q
- Allows transport against a NADH gradient
- Prevent in muscle
How do the charged ATP and ADP ions exit and enter matrix?
Via the ATP-ADP Translocase
Electron transport _____ energy; ATP synthesis ____ energy
Releases; Requires
Inhibition of which components of the electron transport chain will stop ETC.
ATP-ADP translocase and ATP synthase
Where do electrons from Cytochrome C go?
O2
Which ion is essential to ETC?
Fe
Which complex contains a heme group that does not receive electrons but protects against formation of reactive oxygen species (ROS)?
Complex II (succinate- Q reductase)
Q pool consists of ___ and ____
Q and QH2
Examples of inhibitors of ATP-ADP translocase
Atractyloside , bongkrekic acid
Some organisms can uncouple electron transport from ATP synthesis to generate_____.
Heat
_______ and ATP synthesis are usually tightly coupled.
Respiratory Chain
Complex II
- Succinate- Q reductase
- Receives electrons from FADH2
- Does not pump electrons
- Contains flavoprotein succinate dehydrogenase
- Transfers electrons to Coenzyme Q
Complex 1
- NADH-Q oxidoreductase
- Receives electrons from NADH
- Pumps four protons
- Transfers electrons to coenzyme Q
- Contains Flavin mononucleotide
Chemical uncoupler example
2,4- dinitrophenol
Brown adipose tissue
a. Rich in mitochondria
b. Contains uncoupling proteins
c. Protons allowed to flow back down into gradient back into matrix
d. ATP disrupted
Components of Electron Transport Chain
- Electrons passed down chain in order of increasing ________ potential—highly __________process
- Energy released ultimately fuels synthesis of ________
- Three large complexes that pump electrons
–Complex I: __________
–Complex III: ______________
–Complex IV: __________
•Complex II:_______________
–Contains ______________
–Does not pump protons
- Electron carriers Coenzyme Q (ubiquinone) and cytochrome c
- The ____________ is a supramolecular complex involving complexes I, II and III
- Ultimate e- acceptor is_________
reduction; exergonic
ATP
NADH-Q oxidoreductase
Q-cytochrome c oxidoreductase
cytochrome c oxidase
succinate-Q reductase
flavoprotein succinate dehydrogenase
respirasome
oxygen
NADH-Q Oxidoreductase (Complex I, or NADH Dehydrogenase)
- Accepts electrons from _____________; donates to ___________
- The reaction:
- Pumps __________ protons
- 2 protons used to form__________
Source of NADH: ____________, ____________, and _________________
NADH; Q
Four
QH2
TCA cycle, fatty acid b-oxidation, amino acid catabolism
Complex II (Succinate-Q reductase complex)
- Contains TCA cycle flavoprotein succinate dehydrogenase
- Pair of e-’s passed from flavoprotein sequentially to 3 Fe-S centers, then to Q
- Irons cycle between +2 (reduced) and +3 (oxidized)
- Contains heme group (heme b) that does not receive electrons, but protects against formation of ____________
- Does not pump protons
- Receives e-’s from the _____________ or ____________
ROS
flavoproteins acyl-CoA dehydrogenase; glycerol-3-phophate reductase
•ATP synthesis is coupled to e- transport via a ____________ across the mitochondrial _____________
proton gradient;inner membrane
Role of Proton Gradient is to RELEASE ATP Formed on ________ of F1
•Observation from isotope exchange experiments: enzyme-bound ATP readily formed in absence of __________
–Gradient not needed to synthesize ATP
- Why is ATP synthesis completely reversible?__________________
- Role of gradient is not to from ATP but to drive its __________
Coupling between respiratory chain and ATP Synthesis is____________
b Subunit
proton gradient.
ATP synthase binds ATP more tightly, stabilizing ATP relative to ADP, shifting equilibrium
release
“obligatory”
ATP Synthase Nucleotide Binding Sites Not Equivalent
•3 b subunits, so 3 active sites (only _______ is catalytically active)
–At any given moment, sites not equal:
- T: tight (_______________)
- O: open (____________)
- L: loose (__________)
- Rotation of g subunit, driven by _______ force, drives interconversion of sites
- No two sites ever in same conformational form
- ATP can be synthesized and released by driving rotation of ________subunit in correct direction
b
binds ATP very tightlycan bind or release ADP or ATP
binds ADP, Pi
proton motive
g
How does proton flow through F0 drive rotation of the g subunit?
- The F0 “a” subunit is _____________while the “c” subunits form a membrane-spanning ring that can ____________
- “a” subunit contains two __________ half-channels that do not span the membrane
–Each half-channel interacts with one “c” subunit
–____________ residue in center
- In proton-rich environment (_________side), proton will enter ½-channel and bind to Asp-61
- “c” subunit then moves in a circle until Asp-61 is in proton-poor environment (_________) of other ½-channel—H+ released to matrix side
- Movement of protons through ½-channels powers rotation of c-ring
- Each proton moves across membrane by “riding around” –like a merry-go-round—on the c-ring
- Important: c-ring is tightly linked to ____ and ___subunits
stationary (stator)
rotate (rotator)
hydrophobic
Aspartic acid
cytoplasmic
matrix
g; e
Shuttles (Transporters, Carriers)
•How do electrons from cytoplasmic NADH enter e- transport chain?
–Inner membrane impermeable to ____________
–Glycerol-3-phosphate shuttle (prevalent in ________)
- mitochondrial glycerol-3-phosphate dehydrogenase (uses _______)
- Present on outer_____________surface of inner membrane
- Donates electrons to_______
- “P/O ratio:” Only __________molecules of ATP formed per e- pair
- Allows transport against an _____ gradient
–Malate-aspartate shuttle (prevalent in ________ and __________)
- Results in movement of pair of electrons from NADH across membrane into matrix—donates e-’s to complex _______
- “P/O ratio:” _______ molecules of ATP formed per e- pair
–Malate-aspartate and glycerol-3-phosphate shuttles operate only under _______ conditions
•How does ATP4- exit, and how do ADP3- and phosphate enter, matrix? How many protons are required?
________________
NADH
muscle
FADH2
(cytoplasmic)
Q
1.5
[NADH]
heart; liver
I
2.5
aerobic
–Via the ATP-ADP translocase and the phosphate translocase; one
•No direct transporters for __________, __________, and __________
NADH, acetyl-CoA and oxaloacetate
Respiratory Chain and ATP Synthesis Usually Tightly Coupled
- ___________ moles of ATP made per mole of glucose
- ETC and ATP synthesis usually tightly coupled
–Rate of flow dependent on _________, ________, _________
–Likewise, TCA cycle shuts down if no ATP synthesis occurs
–Rates of ETC and TCA cycle regulated by rate of ATP synthesis—based on need for energy
•Some organisms can uncouple e- transport from ATP synthesis to generate________
–Brown adipose tissue
- Rich in mitochondria
- Contains lots of ________ protein
- Protons allowed to flow down gradient, back into matrix
–__________ synthesis disrupted
Thirty
ADP, Pi, and O2
heat
uncoupling
ATP
Inhibitors of OXPHOS
•Inhibition of e- transport chain
–___________ and __________: block e- flow through complex I (but flow thru II possible)
–_________: blocks flow through complex III
–_______, _________, and __________: inhibit cytochrome oxidase
- Inhibition of ATP synthase by _________ and ___________
- Example of chemical uncoupler:_____________
–e- transport can proceed, but ATP synthesis cannot
•Inhibition of ATP-ADP translocase by _________ and ______________
Rotenone, amytal
Antimycin A
CN-, N3- (azide), CO
–Oligomycin, dicyclohexylcarbodiimide
2,4-dinitrophenol
–Atractyloside, bongkrekic acid