Human mitochondria and mtDNA

HUMAN MITOCHONDRIA


Functions of Mitochondria

1. Mitochondria are the "powerhouses" of the cells as they are the site of Oxidative Phosphorylation (OXPHOS) and ATP production (generation of ATP). 
2. Mitochondria are required for cell proliferation. Lack of mitochondria leads to no cell proliferation. Cells cannot reproduce without mitochondria.
3. Mitochondria are responsible for programmed cell death (apoptosis)  - This will be studied in Year 2 Medicine. 

Unwanted Activities of Mitochondria

1. Mitochondrial activity is also responsible for the (unwanted) generation of reactive oxygen species (ROS) which are implicated in neurogenerative diseases, metabolic diseases and also many types of cancer.
2. Mitochondria are associated with the development and progression of cancer.

Mitochondrial Nucleic Acids

1. Mitochondrial nucleic acids resemble bacterial nucleic acids

Mitochondrial DNA (mtDNA)

1. Mitochondrial DNA (mtDNA) is present in mitochondria
2. Mitochondrial DNA (mtDNA) is circular
3. MtDNA is 16,569 basepairs (bp) (or approx. 16,500 nucleotides)
4. MtDNA is present as multiple copies within an individual cell
5. MtDNA encodes 13 essential polypeptides which are part of the OXPHOS complexes, as well as 22 tRNAs and 2 rRNAs
6. MtDNA has information to code for the synthesis of 2 ribosomal RNAs (rRNAs), 22 tRNAs and 13 proteins, all of which are components of the electron transport chain (ETC)
7. Most mitochondrial proteins are encoded by nuclear DNA (nDNA) and are synthesized in the cytoplasm

Dichotomy of Mitochondrial Metabolism

1. Some mitochondrial protein synthesis is under the control of mitochondrial DNA (mtDNA)
2. Important proteins of the outer membrane of the mitochondria  are synthesized under the influence of nuclear DNA (nDNA)

External Links

1. Wikipedia. Mitochondria
2. Wikipedia. Cambridge Reference Sequence
3. Nature 290, 457 - 465 (09 April 1981); doi:10.1038/290457a0. Sequence and organization of the human mitochondrial genome

Textbook

Textbook of Biochemistry (For Medical Students), Third Edition, 2004, p416.