Power, Sex, Suicide: Mitochondria and the meaning of life - Nick Lane
August 08, 2014
Great book! The book is wonderfully detailed and complicated (in a good way). Given the intricate subject matter, I found it wonderfully clear, like a good detective story. After all, any science is at it's heart, a detective story!
The epilogue is a great summary of the entire book and I might be returning to it to refresh myself in a year's time.
Notes for myself:
The energy pump
The mitochondria (and chloroplast) generate energy in a similar way to a hydroelectric dam by pumping electrons to generate a proton gradient across their cell membrane. This gradient is used for lots of things, perhaps most importantly, to generate ATP in the ATPase situated along the cell wall.
What role does the cell wall play?
In prokaryotes, it is essential to maintain a proton gradient by keeping the outside of the cell acidic in order to generate energy (and ATP), among other functions. In eukaryotes, this is done by the mitochondria so there is no need for a cell wall.
Why do bacteria have so many genes and are so small compared to eukaryotes?
Energy produced is proportional to surface area so want small size. In the case of eukaryotes, they can just increase the number of mitochondria!
Also, bacteria replicate very quickly under high selective pressure so need to minimize genes (the negatives of which are counteracted by lateral gene transfer). In the case of eukaryotes, they can out compete by predation opportunities afforded by the greater size and versatility.
Sex and aging
Sex and aging are similar and are both mechanisms to repair faulty genes and cells respectively. When cell fusion happens, the genes in the nucleus recombine but what about the mitochondrial genes? They have to be matched to the genes in the nucleus so it's easier to just keep one copy which is why only females pass down the mitochondria. This is also why it's easiest to only have two sexes.
Free radical theory of aging
Free radical leak happens in the process of the electron pump. These free radicals are used to control the production of energy and maintain the health of mitochondria from the nucleus but free radicals also cause mitochondrial dna to mutate over time which damages them.
The cell reacts to this by killing the mitochondria that are damaged past a limit and boosting the production of the others. However, over time all the mitochondria might be damaged beyond saving and in this case the body has no choice but to terminate the cell. This leads to tissue damage and causes degenerative diseases.
To fix this, the best thing would be to slow down the leak of free radicals. This can be done for instance by creating higher demand for energy so that the pump works smoothly which explains why athletes are fitter and age slower.