5- Mitochondria And Oxidative Phosphorolation

Question 1

What is the evidence for mitochondria evolving from prokaryotes

Answer 1

Mitochondria can only arise from pre existing mitochondria and chloroplasts
Mitochondriapossesstheirowngenomeanditresemblesthatofprokaryotes,beingasingle circular molecule of DNA, with no associated histones
Mitochondria have their own protein synthesizing machinery, which again resembles that of prokaryotes, not that of eukaryotes
Thefirstaminoacidoftheirtranscriptsisalways fMet asitisinbacteriaandnot
(Met) that is the first amino acid in eukaryotic proteins
Anumberofantibiotics(e.g.,streptomycin)thatactbyblockingproteinsynthesisinbacteria
also block protein synthesis within mitochondria and chloroplasts. They do not interfere with protein synthesis in the cytoplasm of the eukaryotes

Question 2

What happens to the redox potential along the etc

Answer 2

electron carriers’ redox potentials increase as you go along the chain, meaning they donate electrons to each other in succession:

Question 3

Describe how atp synthase generates atp

Answer 3

When protons flow through the membrane via a pore, the disc of the c subunits are compelled to rotate
the γ subunit of the F1 unit rotate, as they are fixed to the c subunit disc
However, the α and β subunits in the F1 unit canot rotate, as they are locked in a fixed position by the b subunit of the F0 unit
As the γ subunit functions as an asymmetrical axle, the β subunit is compelled to undergo structural changes. This rotation drives transitions of the catalytic portions of the β subunits, which in turn, alters their affinities for ATP and ADP
As a consequence, torsional energy flows from the catalytic subunit into the bound ADP and Pi, to promote the formation of ATP

Question 4

Which subunits of atp synthase rotate

Answer 4

C and gamma

A,b, alpha, beta are fixed

Question 5

Describe some metabolic poisons

Answer 5

Cyanide: binds to Fe3+ in cytochrome oxidase blocking etc
CO: binds to Fe2+ in cytochrome oxidase blocking etc
Oligomycin: antibiotic with binds to ATP synthase stalk, so no proton flow+ atp synthesis
DNP: uncoupled ETC from atp synthase by allowing protons through membrane