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Lecture 8
Mitochondria
| Question | Answer |
|---|---|
| Mitochondria | 1. site of aerobic respiration 2. relatively large organelle 3. contain own DNA 4. contain own ribosomes 5. self replicating via binary fission 6. has double membrane |
| endosymbiont theory | mitochondria and chloroplast arose in eukaryotes as phagocytized prokaryotes |
| mitochondrial replication | follow mtDNA replication, undergo a process similar to binary fission |
| Endosymbiont Theory | 1. early atmkosphere had no O2 2. photosynthetic microbial organisms began to evolve 3. increased O2 in the atmosphere 4. aerobic bacteria evolved |
| protoeukaryotes | early ancestor of eukaryotes-evolved the ability to ingest materials via phagocytosis- phagocytized the aerobic process |
| protoeukaryote and aerobic bacteria | developed a mutualistic relationship; aerobic bacteria survive within a protected env. protoeukaryote- new source for ATP by aerobic respiration |
| protoeukaryotic evolution | 1. bacteria became permanent residents 2. retained during cell division 3. some genes lost from bacteria 4. perhaps some transferred to the host genome |
| outer mitochondrial membrane | derived from the vesicle membrane |
| inner mitochondrial membrane | derived from the bacterial plasma membrane |
| mitochondrial structure | 1. outer mitochondrial membrane 2. inner mitochondrial membrane 3. intermembrane space 4. matrix |
| Matrix | mtDNA, ribosomes, krebs cycle enzymes |
| mitochondrial transporters | How does ATP get out of the mitochondria to the cytoplasm where its needed? |
| electric or acid/base gradients | help move substrates in and out of the matrix |
| inner membrane transporters | NAD/NADH are shuttled across the inner membrane via specific shuttles |
| specific inner membrane shuttles | 1. glycerol phosphate shuttle 2. malate aspartate shuttle |
| outer membrane movement | occurs freely through large pores like VDAC |
| outer membrane functions | phospholipid synthesis fatty acid desaturation fatty acid elongation |
| inner membrane functions | electron transport oxidative phosphorylation metabolite transport |
| matrix functions | pyruvate oxidation TCA cycle Beta oxidation of fats DNA replication,transcription and translation |
| if the function of ATP synthase is dependent upon a proton gradient across the inner membrane, how is the H+ gradient maintained for ATP synthesis? | 1. the cristae could not be connected to the inner membrane. 2. the cristae exist as a separate membrane system, connected at cristal junctions 3. baffle model-proton gradient across the cristae membrane is not direcly adjacent to the mitochondrial memb |
| three compartment model | 1. outer mitochondrial membrane 2. inner mitochondrial membrane 3. cristae membrane 4. intermembrane space 5. intercristal space 6. matrix |
| mitochondrial DNA | 1. circular DNA 2. humans; 16500 bp 3. 37 genes=13 involved in mitochondrial respiratory function |
| mitochondrial genome encodes for | 2- rRNA 22- tRNA 13- polypeptides protein complexes |
| mitochondrial DNA | 1. complex I: NADH dehydrogenase 2. complex III: coenzyme Q-Cyt. C oxidoreductase 3. complex IV: cytochrome C oxidase 4. ATP synthase |
| complex IV | has 13 subunits: 3 are encoded by mtDNA 10 are encoded by nuclear DNA |
| cytochrome respiratory complexes | complex 1,2,3,4,5 |
| How are the 2 genomes coordinated? | via a few specific transcription factors(NRF-1)that are all encoded by the nuclear genome also by a transcription factor co-activator (PGC-1) |
| NRF-1 (nuclear respiratory factor-1) | is a nuclear encoded transcription factor that activates the expression of nuclear genes required for mitochondrial respiratin,heme biosynthesis and mitochondrial DNA transcription and replication |
| NRF-2 (nuclear respiratory factor-2) | similar to NRF-2 |
| T-fam (transcription factor A of mitochondria) | is a nuclear encoded transcription factor that activates the expression of mitochondrial genes required for mitochondrial respiration |
| TFB1M and TFB2M | mitochondrial transcription factors B1/B2 |
| calcineurin | is a nuclear encoded calcium activated phosphatase |
| NFAT (nuclear factor of activated T-cells) | is a nuclear encoded transcription factor that translocates to the nucleus upon dephosphorylation by calcineurin. activates the expression of various nuclear encoded mitochondrial proteins. |
| PGC-1 (peroxisome proliferator activated receptor gamma coactivator-1) | is a nuclear encoded transcritional coactivator that assists PPARy in activating gene transcription of nuclear encoded genes related to mitochondrial function |
| conditions when requirement for mitochondria is needed | 1. endurance training 2. cell growth 3. elevated thyroid hormone 4. thermmogenesis of brown fat |
| How do the proteins get into the mitochondria? | 1. TOM/TIM complexes 2. TOM= translocase of outer membrane 3. TIM= translocase of inner membrane 4. nuclear encoded mitochondria proteins generally have an aminoterminal mitochondrial transit sequence |
| mitochondrial protein import | 1. hsp70 chaperone binds to polypeptide 2. the transit sequence binds to TOM receptor 3.Hsp 70 molecules detach as polypeptide passes through membranes 4. transit sequence cleaved 5. Hsp 70 molecules bind and release polypeptide as it enters matrix |
| mitochondrial dysfunction | nuclear and mtDNA mutations cause inherited diseases that involve muscle or neural function |
| mitochondrial myopathy (MELAS)encephalopathy lactic acidosis-stroke syndrome | caused by mutations in the mt genes encoding ADH dehydrogenase and mitochondrial tRNA |
| maternally inherited MELAS symptoms | lactic acidosis, muscle weakness, transient paralysis, repeated strokes |
Created by:
aareynolds
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