Summary Easy to understand notes on respiratory chain and oxidative phosphorylation

Respiratory chain and oxidative phosphorylation - Binding change mechanism

Mitochondria Respiratory chain provides most of the energy captured during
catabolism through oxidative phosphorylation (90%)
- Powerhouse of the cell
- Where capture of free energy happens Respiration control ensures a constant supply of ATP
- Respiration will generate ATP thru oxidative
phosphorylation - Oxidation and phosphorylation are tightly coupled.
- Has a double membrane Oxidation cannot proceed via the respiratory chain
o Outer is permeable to most metabolites without concomitant phosphorylation of ADP
 Acyl-CoA synthetase - States of respiratory control
 Glycerol phosphate acyltransferase 1. Availability of ADP and substrate
o Inner is selectively permeable 2. Availability of substrate only
 Necessitates exchange transporters 3. Capacity of the respiratory chain itself, when
 Cardiolipin all the substrates and components are present
 Enzymes of respiratory chain in saturating amounts
 ATP synthase 4. Availability of ADP only (most cells in the
 Membrane transporters resting state)
5. Availability of oxygen only
Respiratory chain
Many poisons inhibit the respiratory chain
- Oxidizes reducing equivalents
- Acts as proton pump 1. Barbiturates – complex I
- Collects and transports reducing equivalents, directing 2. Antimycin A and dimercaprol – complex III
them to their final reaction with oxygen to form water 3. H2S, carbon monoxide, cyanide – complex IV
- Oxidative phosphorylation 4. Malonate – complex I
o Liberated free energy is trapped as high- 5. Atractyloside – transporter of ADP to ATP out of the
energy phosphate mitochondrion
6. Oligomycin – blocks flow of protons through ATP
Components of the respiratory chain are contained in 4 large synthase
protein complexes embedded in the inner mitochondrial 7. Uncouplers – dissociate oxidation in the respiratory
membrane chain from phosphorylation
a. 2,4-dinitrophenol – most used uncoupler
4 large protein complexes b. Thermogenin – in brown fat
- NADH-Q oxidoreductase or Complex I Exchange diffusion systems involving transporter proteins that
- NADH to coenzyme Q or ubiquinone span the membrane are present in the membrane for exchange
- Q-cytochrome c oxidoreductase or Complex III of anions against OH- ions and cations against H+ ions.
- Passes electrons to cytochrome c
- Cytochrome c oxidase or Complex IV Ionophores
- Passes electrons to oxygen then forming
water - Lipophilic molecules that complex specific cations
- Succinate-Q reductase or Complex III - Facilitate transport of specific cations through biologic
- For substrates with more positive redox membranes
potentials than NAD+/NADH - Valinomycin
- Instead of Complex I - Dinitrophenol

Flavoproteins & Iron-Sulfur Proteins (Fe-S > single electron Energy-linked transhydrogenase
transfer reactions) are components of the respiratory chain
- Protein in the inner mitochondrial membrane
complexes I, II, and III
- Couples the passage of protons down the
Q accepts electrons via complexes I and II electrochemical gradient

The Q cycle couples electron transfer to proton transport in Oxidation of extramitochondrial NADH is mediated by substrate
complex III shuttles

- Electrons are passed from QH2 to cytochrome c via - Substrate pairs – transfer of reducing equivalents
complex III through mitochondrial membrane
- Glycerolphosphate shuttle
Molecular oxygen is reduced to water via complex IV - Malate shuttle – more universal

Chemiosmotic theory Ion transport in mitochondria is energy linked

- Electron transport via the respiratory chain creates a The creatine phosphate shuttle facilitates transport of high-
proton gradient which drives the synthesis of ATP energy phosphate from mitochondria
- Proton motive force is the driver
- Complex I, II, and III acts as proton pumps Fatal infantile mitochondrial myopathy and renal dysfunction –
- Can account for respiratory control and the action of severe diminution or absence of most oxidoreductases of the
uncouplers respiratory chain

ATP Synthase MELAS

- Membrane-located - inherited condition due to Complex I or IV deficiency
- Forms ATP in the presence of Pi + ADP - may be involved in Alzheimer disease and diabetes
- Several subunits of the protein form a ball-like shape mellitus
arranged around an axis known as F1