Ch_11_Mitochondria - MITOCHONDRIA Most mitochondrial...

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MITOCHONDRIA Most mitochondrial proteins translated on free cytosolic ribosomes Also contain their own DNA o Encodes tRNA, rRNA, and mitochondrial proteins Mitochondria surrounded by double layer membrane. o Sac in another sac, but NOT an envelope b/c the two never touch o Inner membrane Many folds (cristae) extending into matrix Main site for ATP generation Impermeable to most ions and small molecules Maintains proton gradient Need biochemical permission to enter matrix o Translocases - all translocases that move metabolites are made of carrier proteins o Bigger transmembrane channels not called carrier proteins o Outer membrane Highly permeable to small molecules Contains porins - channels allowing passage of molecules smaller than 1000 daltons. o Matrix Where Krebs Cycle occurs and some mitochondrial encoded proteins are synthesized Mitochondrial genetic system Mitochondria maybe evolved from bacteria with symbiotic relationship with host o ENDOSYMBIOSIS Mitochondria have circular DNA. o Present in multiple copies per organelle o Encode only a small number of proteins essential for oxidative phosphorylation o Encode all ribosomal RNAs and most of transfer RNAs needed for translation of these protein-coding sequences within mitochondria. o Human mitochondrial DNA encodes 16S and 12S rRNAs and 22tRNAS required for translation of proteins encoded by the organelle genome. o 2 rRNAs are the only RNA components in mitochondrial ribosomes. o Many tRNAs able to recognize more than a single codon in mRNA because of wobble. Rampant wobbling in mitochondria U in anticodon of tRNA can pair with any of 4 bases There are exceptions to universal code UGA= tryptophan AGA, AGG= stop AUA= Methionine (start)
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o Mitochondria of fertilized eggs contributd by oocyte rather than sperm Mitochondrial DNA inherited by MOTHER! o Mutations of mitochondrial DNA can occur, causing disease tRNA mutation- metabolic syndrome mutation of e- transport chain DNA- can cause Leber’s hereditary optic neuropathy. Progressive mutations contributes to process of aging. Protein import/Mitochondrial assembly Genes encoding proteins required for replication and expression of mitochondrial DNA are contained in nucleus Nucleus contains genes encoding most mitochondrial proteins required for oxidative phosphorylation and all enzymes involved in metabolism. Over 95% of mitochondrial proteins synthesized on free cytosolic ribosomes and
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Ch_11_Mitochondria - MITOCHONDRIA Most mitochondrial...

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