A must read new book by Nick Lane - The Vital Question: Why is life the way it is? and a great review here
Living cells are powered by a totally unexpected process. The energy from food is used to pump protons across a membrane to build up an electrochemical gradient. This gradient drives the machinery of life, like water from a dam driving a turbine.
And Lane argues that life has been powered by proton gradients from the very beginning. Forget all those primordial soups or "warm ponds": only the natural proton gradients found in undersea alkaline hydrothermal vents could have provided the continuous flux of carbon and energy that life requires. These vents may be common on rocky planets so, if this reasoning is correct, simple cells should be too.
It's the next step that is tricky. To
become more complex, cells need more membrane to provide more energy.
But the larger the area of membrane, the harder it is to keep control of
the proton gradient – and losing control means death. So cells stayed
simple. "There is no innate or universal trajectory towards complex
life," Lane writes.
Not, at least, until something extraordinary happened: one kind of simple cell somehow started living inside another. Eventually, the first cell turned into the self-contained energy-producing structures we call mitochondria. This Russian-doll arrangement meant cells could get more energy simply by making more mitochondria, allowing them to become much larger and more complex.
Not, at least, until something extraordinary happened: one kind of simple cell somehow started living inside another. Eventually, the first cell turned into the self-contained energy-producing structures we call mitochondria. This Russian-doll arrangement meant cells could get more energy simply by making more mitochondria, allowing them to become much larger and more complex.
But learning to live together was far from
easy. The first complex cells were forced to evolve features such as
sexual reproduction and DNA wrapped up in a membrane to survive. In
other words, the acquisition of mitochondria wasn't just necessary for
cells to become complex, it shaped their entire nature – and it still
does. Our lifespans are determined by our mitochondria, Lane argues, but
not because they produce free radicals, as we once thought.
It sometimes seems that there are few big ideas in biology any more, that it's all about specialists crunching data. But this is a book of vast scope and ambition, brimming with bold and important ideas. I do hope some of them are wrong, because it's disappointing to think that alien life consists mostly of slime, or that it will be very difficult to extend our lifespans beyond about 120 years.
It sometimes seems that there are few big ideas in biology any more, that it's all about specialists crunching data. But this is a book of vast scope and ambition, brimming with bold and important ideas. I do hope some of them are wrong, because it's disappointing to think that alien life consists mostly of slime, or that it will be very difficult to extend our lifespans beyond about 120 years.
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