Mitochondria and Oxygen Metabolism Flashcards
How many total mitochondrial genes are there, and how many of these are encoded for by mDNA?
683 genes in mitochondria
13 genes come from mitochondrial genome
How do most (98%) of proteins enter the mitochondria?
Import machinery
what bacteria do mitochondria show a strong relationship to and why is this so?
- alpha proteobacteria
- mitochondria were acquired through endosymbiotic event
T or F: the outer membrane of the mitochondria is fairly permeable.
True, it is porous to small molecules up to 5000 Da
T or F: the inner membrane is permeable to ions.
False, very impermeable to ions, especially protons
Where does cytochrome c reside?
in the intermembrane space
What important structures are held in the inner mitochondrial membrane?
- Electron transfer complexes
- ATP synthase
- Carrier proteins to exchange metabolites between cytosol and matrix
Describe the structure of cristae.
Tubes and flattened sacs with limited connections to the portion of the inner membrane that lines the outer membrane
- Small openings to the inner membrane space may limit diffusion of metabolites like ADP and ATP
T or F: the state of the cristae changes in response to physiological conditions.
True, in times of high energy consumption/ATP production they fuse to allow for easier diffusion of particles
What is the difference in state 3 and 4 respiration.
State 3 - active state of respiration, lots of ADP and O2 being used up
State 4 - Resting state respiratoin, little ADP and very little O2 being used up
What happens to the cristae in active state 3 and why?
- There is is fusion of the cristae
- Fusion may open bottlenecks to diffusion and allow rapid exchange of metabolites with the cytosol
What protein has been linked to cristae morphology and why?
- mitofillin
- part of MINOS (mitochondrial inner membrane organizing system)
**These play a critical role in dynamic changes that take place in the mitochondrial structure during respiration
What happens when the gene coding for mitofillin is knocked out?
mitochondrial inner membranes appear like layers of an onion but they are not connected to each other or to inner boundary membrane
Explain how mitochondria are important in apoptosis.
- Bad, Bax, or Bid binds to mitochondrial receptor and causes the membrane to become leaky
- Cytochrome C leaks to the cytosol
- Cytochrome C unites with Apaf-1
- Cyto C + Apaf-1 recruit caspase 9
Note: caspases are cystein proteases that must be activated
T or F: the outer membrane of the mitochondria is similar to the outer membrane of the cell.
True
T or F: the protein to lipid ratio is about 1:1 by weight on the outer mitochondrial membrane
True
Can BID cause changes in the shape of the cell cristae?
- It has been indicated that it does
- Mouse liver treated with trucated BID showed a dramatic effect on the cristae
What allows the outer membrane to be porous to small molecules?
Porin Channel proteins
T or F: the inner membrane has a higher protein to lipid ratio than the outer membrane.
True, its 3:1
What phospholipid is unique to the inner membrane and what does it do?
- Cardiolipin - unique to the inner membrane
- Its associated with many of the membrane complexes and is required for optimal function
What disease results from a defective cardiolipin biosynthesis gene?
- Barth symdrome
- Results in defective mitochondria causing cardiomyopathy and muscle weakness
How does the inner membrane get things like ADP and pyruvate from one side of the membrane to the other?
- Antiporters
What does ADP/ATP antiport depend on?
- membrane potential
- charges on the substrates
Why do diseases of mitochondrial origin often result in the production of reactive oxygen species?
- mitochondrial enzymes work to reduce oxygen to water
- If one of these enzymes functions incorrectly then one of the reduced intermediates of oxygen can be released causing damage to the cell
What enzyme exists in the mitochondria to eliminate superoxide (ROS), what disease results from a defect in this enzyme?
- superoxide dismutase
- Lou Gehrig’s disease (cytosolic form)
What enzyme reduces H2O2 to water and O2?
Catalase (found in mitochondria and also in blood cells)
Name two free radical scavengers that protect against the hydroxyl radical (ROS).
Vitamin C and E
What would you expect to happen if the proton gradient in the mitochondrial membrane were to be uncoupled?
- This proton gradient would dissipate
- ATP would not be made to work in feedback inhibition
- Heat would be generated
How does heme get into RBCs?
- Made in the mitochondria of RBCs before they loose all of their organelles
How do ribosomes and proteins enter the mitochondria?
- Mitochondria must import proteins (NOT THROUGH CARRIERS)
- doesn’t need to import RNAs because they are encoded for in the ribosome
Where are porins located?
The outer membrane
Where is cardiolipin located?
inner membrane
Where is mitofilin found?
- inner boundary membrane
Where are mitochondrial carriers located?
On the inner membrane
What is the job of MINOS and what lipid is MINOS dependent on?
- MINOS binds cardiolipin
- acts like a diffusion barrier
- this ensures the protein composition of the inner boundary membrane is different from the cristae membranes
Which membrane becomes leaky as a result of Bad, Bit, or Bax binding that allows cytochrome c to escape?
Outer membrane
