Mitochondrial respiratory chain Flashcards
Outer/Inner membrane permeability
Outer membrane: Freely permeable to small molecules and ions
Inner membrane: Impermeable to small molecules and ions, including H+
Complex I [4]
Electrons passed from FMN to produce FMh2
Transfer to series of iron-sulphur clusters
Transfer to coenzyme Q or ubiquinone
Proton pumps, moves protons from matrix into intramitochondrial space
Complex II [4]
Succinate dehydrogenase
Electrons from FADh2 pass electrons to CII
CII pass them to ubiquinone
Other substrates for mitochondrial dehydrogenase also pass their electrons to ubiquinone but not through CII - e.g. G3P shuttle
Complex III [2]
Ubiquinone cytochrome C oxidoreductase
2nd of 3 proton pumps in respiratory chain
Complex IV [4]
Cytochrome oxidase
3rd and final proton pump
Carries electron from cytochrome C to molecular O2
Produce water
Synthesis of ATP [3]
Inner mitochondrial leaflet is generally impermeable to charged species
3 specific systems: Transport ADP and Pi into matrix, Synthesise ATP and Transport ATO into cytosol
Substrates are Mg2+ complexes of ADP and ATP
Adenine Nucleotide Translocase [4]
Integral protein of inner mitochondrial membrane
Transport ADP3- from intramitochondrial membrane space into matrix
In exchange for ATP41 molecule - transported in other direction & favoured by P pump
Antiporter
Atractyloside
Glycoside isolated from thistle, is a specific inhibitor of adenine nucleotide translocase
Phosphate translocate [3]
2nd membrane transport essential for oxidative phosphorylation and ATP synthesis
Transport both phosphate and H+ into matrix - SYMPORTER
Favoured by transmembrane proton gradient
ATP synthase [2]
An F-type ATPase - 2 functional domains
Fo - oligomycin-sensitive proton channel
F1 - ATP synthase
Fo [3]
Compromises 3 diff subunits: a, b and c
Forms complex of 13-15 subunits
Subunits c1-c10 arranged in circle
F1 [3]
Comprises 5 different types of subunit**
Forms complex of 9 subunits
The 3B subunits have catalytic sites for ATP synthesis
Theory of rotational catalysis [4]
3B subunits take in turns catalysing ATP synthesis
Any B subunit starts in conformation for binding ADP and Pi
Changes conformation - active site now binds ATP tightly
Changes conformation to give active site a very low affinity for ATP so ATP is released
Summary of energy changes
Highly exergonic reactions
NADH + H+ + ½ O2 NAD+ + H2O
Energy released is coupled to movement of H+ across the inner membrane
Electrochemical energy generated represents temporary conservation
