Oxidative Phosphorylation Flashcards
(13 cards)
What does each of the membranes in mitochondria do?
Double membrane= Separates them from the cytoplasm in eukaryotic cells
Both membranes= Bilayers
Outer membrane: Highly permeable with proteins= Porins= Gives access to small molecules whether they are charged or not
Inner membrane: Very limited permeability= Non-porous
Endosymbiotic origin:
Outer= From eukaryotic plasma membrane
Inner= Bacterial plasma membrane
What is the the inner membrane made of? Why is it so important?
Inter membrane space= Separates the outer and inner membrane
Made up of: Matrix, Cristae
Inner: Vital for energy generation, as this is where Oxidative phosphorylation takes place
Most of the reactions of the citric acid cycle (and fatty acid oxidation)= Take place inside the matrix
2 faces of the inner membrane are distinct:
Referred to matrix side (in) and cytoplasmic side (out)
Also referred to as N and P sides as there is an electrical potential across the membrane
How is the mitochondria inherited?
Cells contain multiple mitochondria, with each containing multiple circular DNA molecules (mtDNA)
Inherited: Cytoplasmically= Maternal inheritance
mtDNA varies in size between different organisms
What is the mitochondria’s coding capacity like?
Its residual mitochondrial genome has only limited coding capacity= Lost capacity for independent replication= Rely on products of nuclear genes for many function
BUT: Most have retained genes for components of the energy generation system, transport proteins and components of the mitochondrial protein synthesis system
Why has the mitochondrion retained its own genome and coding capacity?
All mitochondrion have retain a protein synthesis system separate from that of the cytoplasm: Genes show different codon usages= Need to translate these genes
What is the major function of mitochondria?
Acts as machines which are capable of efficiently interconverting different types of energy
-Take reduced cofactors and convert them into a form that can be used to force other reactions in the cell
How many molecules of reduced cofactors and GTP does the TCA cycle produce on its own?
3NADH, 1GTP, 1FADH2 per cycle= Very little ATP on its own
What does the process of oxidative phosphorylation do?
GENERATES ATP Reduced cofactor (NADH or FADH2) get oxidised= transfers electrons to a series of electron carriers Immediate energy sources that power ATP synthesis are proton gradient + Electrical potential (voltage gradient) across membrane= Collective called proton-motive force
Final reduced carrier donates 2 electrons to oxygen which then forms water
What is the proton motive force generated by?
Generated by stepwise movement of electrons by electron carriers that leads to pumping of proteins out of the mitochondrial matrix
Oxidation of NADH and phosphorylation of ADP are coupled by a generation of proton gradient
Coupling: Electrons do not flow from NADH or FADH through the electron transport chain to oxygen unless ADP is simultaneously phosphorylated to ATP
Respiratory control: Only if ADP is available will the electron transport be fast= Ensures that electron flow occurs when ATP synthesis is required
Where did the energy in NADH and FADH2 come form?
Most free energy released when glucose is oxidised to carbon dioxide is retained in the reduced coenzymes
Most of the energy is dissipated as heat
ATP production is maximised by releasing the free energy in small increments in the electron transfer chain
Respiration: Electrons are released from NADH and FADH2 to oxygen:
NADH + H+ + 1/2 O2 —-> NAD+ + H20
How many multi protein complexes does the electron transfer chain contain?
4 multiprotein complexes
3 of these are electron driven proton pumps that create the proton gradient
Transfer of electrons down this chain is driven by redox potential
What do protein complexes do?
They take a reduced cofactor and use it to oxidise another carrier= Becomes reduced
It is then used in another complex to reduce a different carrier= Regenerated= Chain starts again
They allow a series of electrons to travel through a series of protein complexes which releases energy
How does embedding the proteins in the membrane make electron transfer more efficient?
Helps prevent the ‘loss’ of electrons to solution
Movement of electrons can be used to drive processes such as ion pumps= Transfer ions form one side of the membrane to the other against a concentration gradient
