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Matrix of mitochondria have very (high/low) concentration of proteins
High
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Inner membrane of mitochondria is highly (permeable/impermeable)
Impermeable (even protons can't get through)
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Outer membrane of mitochondria is highly (permeable/impermeable)
Permeable
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What creates high permeability of mitochondrial outer membrane?
VDACs (voltage dependent anion channels)
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How to isolate mitochondrial compartments
- Suspend mitochondria in medium of low osmolarity
- Influx of water causes inner membrane to swell (impermeable), causes outer membrane to rupture
- Centrifugation leaves contents of intermembrane space in nonsedimenting fraction
- Transfer of the rest of stuff to medium of high osmolarity to cause shrinkage - leaves you with mitoplast (mitochondria minus outer membrane) and small vesicles from ruptured outer membrane
- Density-gradient centrifugation separates outer membrane from mitoplast
- Disruption and centrifugation of mitoplast separates inner membrane from matrix
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3 parts of inner membrane of mitochondria; how they differ in structure and function
- Cristae membrane: part of the folds; rich in proteins involved in cell respiration
- Cristae junctions: between cristae membrane and inner boundary membrane; contain MINOS
- Inner boundary membrane: not part of the folds; rich in proteins involved in protein transport
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Mitoplast
Mitochondria minus outer membrane
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MINOS in mitochondria
- Mitochondria Inner Organizing System
- Located in cristae junctions on inner membrane
- Involved in generation of cristae and connect inner membrane to outer membrane
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What happens to mitochondria with mutant MINOS?
Inner membrane not connected to outer membrane and no cristae junctions
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Lipids of mitochondria
- Phosphatidylcholine
- Phosphatidylethanolamine
- Cardiolipin (mitochondria-specific phospholipid on inner membrane, with 4 fatty acids instead of 2, 2 glycerol groups, 2 phosphates, and anionic)
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Mitochondrial division is (reversible/irreversible)
- Reversible
- Fusion and fission are always happening
- There is an equilibrium between fusion and fission
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Cardiolipin
- Mitochondria-specific phospholipid located on inner membrane
- 4 fatty acids instead of 2; 2 glycerols; 2 phosphates; overall negative charge (anionic)
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3 diseases associated with changes in mitochondrial structure and function
- Diabetes
- Neurodegenerative diseases (Parkinson)
- Aging
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Complexes on inner mitochondrial membrane contain proteins encoded by (mtDNA/nDNA/both); except for one complex (which one?), which contains proteins encoded by (mtDNA/nDNA/both)
- Both
- Except Complex II
- Only nDNA
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Common features in diseases caused by mitochondrial DNA mutations
- Myopathy
- Cardiomyopathy
- Neuropathy
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3 unique aspects of mitochondrial genetics
- Maternal inheritance
- Heteroplasmy
- Mitotic segregation
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Why is mtDNA maternally inherited?
- Sperm injects nDNA into oocyte, but not mtDNA
- Why? Sperm mitochondria have high ATP production for motility, oocyte mitochondria does not need that
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Heteroplasmy
- Multiple copies of mtDNA in each cell
- There can be a coexistence of mutated and normal mtDNA
- At least 50% of the cell's mitochondria need to have the mutant DNA in order for disease phenotype
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Mitotic segregation of mtDNA
- Since there is a random distribution of organelles during cell division, there is a non-equal distribution of normal and mutated mtDNA among daughter cells
- So, there is a variable clinical presentation of mitochondrially inherited diseases
- Clinical presentation changes with age because as cells continue to divide, distribution of mitochondria changes
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Mitochondrial DNA encodes how many polypeptides?
13
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