Electron Transport Chain Flashcards
What is the overall mechanism of the electron transport chain
energy released from NADH and FADH2 is used to synthesize ATP
Where does the electron transport chain occur
the mitochondria
Oxidation of reduced factors: ___________
energetics
Reduced cofactors are passed to oxygen ____________ along the electron transport chain
indirectly
Instead of all energy being released at once, what occurs
the reoxidation of NADH and FADH2 is broken into several distinct processes
- results in smaller energy changes
Electron carriers in ETC are arranged in order of…
increasing reduction potential
What is the terminal electron acceptor
oxygen
What is complex 1
NADH dehydrogenase
What is complex 2
succinate dehydrogenase
What is complex 3
acyl-CoA dehydrogenase
What is complex 4
glycerol 3-phosphate
What is another term for coenzyme Q
ubiquinone
If ubiquinone accepts one electron what is formed
semiquinone radical
If ubiquinone accepts two electrons what is formed
the alcohol ubiquonol
How are electrons carried from one ETC complex to another
ubiquinol can freely move in the membrane, so it carries electrons from one complex to another
Cytochrome C are a family of proteins with iron-containing ____________ prosthetic groups
heme
Cytochrome C is a soluble protein found in the _______________ ____________
intermembrane space
What is the function of cytochrome c
shuttles electrons from complex 3 to complex 4
How many electrons does the heme group on cytochrome c carry at a time
one at a time
Complex’s 1 and 2 transfer electrons to Q, reducing it to ________
QH2
QH2 passes electrons to ____________________ through complex 3
cytochrome c
Complex 4 transfers electrons from reduced cytochrome c to _______
O2
Electron flow from complex’s 1,3,4 is accompanied by ____________ __________ from the matrix to intermembrane space
proton flow
In the presence of an electron donor and O2, all carriers occurring before the point of obstruction become _____________ and the carriers beyond the point become ______________
before point; become reduced
after point; become oxidized
Many of the carriers have distinctive optical ___________________ with different optical spectra under oxidized and reduced states
chromophores
What is the importance of the optical chromophores
allows for identification of the redox state of carriers
How many electrons from NADH are pumped
10 total
4 by complex 1, 4 by complex 3, and 2 by complex 4
How many electrons from FADH2 are pumped
6 total
4 by complex 3 and 2 by complex 4 (bypass complex 1)
What is the energy stored in the gradient called
the proton motive force
What are the 2 components of the proton motive force
- chemical potential energy
- electrical potential energy
What causes the chemical potential energy in proton motive force
difference in H+ concentration
What causes the electrical potential energy in proton motive force
separation of charges
Energy is _____________ in the proton gradient
conserved
What is chemiosmotic theory
free energy liberated by redox reactions is used by ETC to pump proteins, moving H+ from matrix to intermembrane space
- energy is stored as an electrochemical gradient
protons flow back into the matrix passively down its concentration gradient through the proton pore of ATP synthase enzyme
The energy of electrochemical gradient is released as is used for the generation of ATP by the ________ _________________ enzyme
ATP synthase
ETC and ATP synthase are _____________
coupled
Chemiosmotic theory readily explains the ______________ between ETC and ATP synthase
coupling
If ETC is blocked, can ATP synthase function?
no
and vice versa
___________ _________________ is an obligatory part of the catalytic cycle
proton translocation
How does the ETC/ATP synthase system become uncoupled
if the integrity of the inner mitochondrial membrane is disrupted, the proton gradient is eliminated
- ETC continues, but ATP synthase stops
*no longer coupled
What is an example of a chemical that acts as an uncoupler
dinitrophenol (DNP)
When DNP is added to the cell, what continues and what stops
ETC continues
ATP synthase stops
What is the mechanism of 2,4 DNP
- the DNP- picks up a proton to form DNPH
- releases the H+ in the matrix forming DNP-
- DNP- crosses back into intermembrane space and negative charge is delocalized over aromatic ring; structure is hydrophobic
- proton gradient is collapsed
- since energy is not conserved by ATP formation, it dissipates as heat
