Electron Transport Chain Flashcards
- ETC is ?
- What drives ATP synthesis?
- All components of ETC and oxidative phosphorylation are present where?
- Transfer of electrons
- Oxidation
- Inner mitochondrial membrane
Main difference in function of the outer and inner membranes of mitochondria?
What is the function of cristae? Location?
Outer membrane has pores that make it freely permeable to most ions and small molecules; inner membrane requires special carriers/transport systems
Cristae increase the surface area of the inner membrane
Inner membrane consists of how many protein complexes? Which are involved in ETC?
5; 1-4
General organization of ETC
Complex I and II are not related, but are both transferring electrons via mobile electron carriers (CoQ, cytochrome c), movement of electrons produces intermediates FADH2 and NADH. These intermediates are high energy but cells cannot use them unless they transfer energy to them to form ATP
Complex I:
- What is complex I called?
- Transfer of electrons from __ to __
- What else is part of complex I?
- NADH dehydrogenase
- NADH to CoQ
- Iron sulfur centers (NADH gives hydrogen to FMN to iron sulfur center)
Complex II:
- Name?
- Transfer of electrons from ___ to ___
- Unique about this complex?
- So how does it differ from complex 1?
- Succinate dehydrogenase
- Succinate to CoQ
- Does not pump protons/does not contribute directly to ATP production
- In complex II there is not movement of hydrogen, there is in complex I though
Both complex I and II transfer electrons to CoQ. What is its structure like?
Accepts electrons and protons from __ and __
Where does CoQ donate its electrons?
Not protein bound, and is the only lipid soluble component of ETC
FMNH2 and FADH2
Cytochrome b (complex III)
What are cytochromes?
Why are various cytochromes able to act at different positions
Membrane bound heme containing proteins
Hemes have slight differences in their standard reduction potentials
Complex III is named?
General overview of ETC so far?
Cytochrome b-c1 complex
CoQ accepts protons separately from complex I and II and takes them to complex III (cytochrome c)
Key features of cytochrome c
Heme containing protein, water soluble, donates electrons to Cu ions of complex IV
Name of complex IV?
Transfer of electrons from __ to __
What is unique about complex IV
Cytochrome oxidase
Cytochrome c to O2
It has the ability to shuttle protons from matrix to intermembrane space (inside to outside)
- ___ has the strongest tendency to gain electrons
2. __ has the strongest tendency to donate electrons
- Oxygen
2. NADH
Oxidative phosphorylation:
Why is oxidation of high energy molecules coupled with phosphorylation of ADP?
Flow of electrons from NADH to oxygen does not directly result in ATP synthesis which is why it has to be coupled with phosphorylation
What is the common intermediate that is coupling oxidation to phosphorylation?
Electrical gradient made by the proton pumps (H+ being transported to intermembrane space causes outside to be more + than inside)
What happens in complex V?
ATP synthase synthesizes ATP using the energy of the proton gradient that was generated by the ETC
Explain the 4 regulations of oxidative phosphorylation:
- Respiratory control
- Substrate shuttles
- Inhibitors
- Uncouplers
- If H+ is not being used for ATP synthesis it builds up, this back pressure inhibits further H+ pumping, electron transport and O2 consumption
- NADH cannot permeate the inner membrane so shuttles are used to transport the reducing equivalents (its energy)
- Inhibitors cause decreased ATP synthesis with decreased O2 consumption and increased NADH
- Uncouples cause decreased ATP synthesis with increased O2 consumption and decreased NADH
If what complex is inhibited, no ATP synthesis will occur
Contrast coupling and uncoupling
Complex IV
Coupling is combining oxidation and phosphorylation, uncoupling the the opposite; uncoupling= no ATP synthesis but increase in O2 consumption means increase in ETC
Is the process of uncoupling and inhibiting the same or opposite?
Opposite
What is a natural uncoupler in the body?
Brown adipose tissue - expresses thermogenin which is a physiological uncoupler protein that dissipates H+ gradient
~ energy is used for generation of heat instead of generation of ATP (hibernating)
