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Posts Tagged ‘enzymes

“To be overly concerned with the original materials, which are merely sentimental souvenirs of the past, is to fail to see the living building itself”*…

The human body replaces its own cells regularly. Scientists at the Weizmann Institute of Science in Rehovot, Israel, have finally pinned down the speed and extent of this “turnover.” About a third of our body mass is fluid outside of our cells, such as plasma, plus solids, such as the calcium scaffolding of bones. The remaining two thirds is made up of roughly 30 trillion human cells. About 72 percent of those, by mass, are fat and muscle, which last an average of 12 to 50 years, respectively. But we have far more, tiny cells in our blood, which live only three to 120 days, and lining our gut, which typically live less than a week. Those two groups therefore make up the giant majority of the turnover. About 330 billion cells are replaced daily, equivalent to about 1 percent of all our cells. In 80 to 100 days, 30 trillion will have replenished—the equivalent of a new you…

Our Bodies Replace Billions of Cells Every Day: “A New You in 80 Days.”

* Douglas Adams, Last Chance to See

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As we sail on the Ship of Theseus, we might spare a thought for Hans Ernst August Buchner; he died on this date in 1902. A bacteriologist, he was a pioneer in the field of immunology, the first to discover a substance in blood, gamma globulins, natural bactericides capable of destroying bacteria.  He also worked with his brother Eduard Buchner, a chemist who won the Nobel Prize in 1907 for his work on fermentation (which helped pave the way for our understanding of the work of enzymes); Ernst had died in 1902, and so did not share in the honor.

source

Emergent-cy…

Scripps Research Institute biologist Gerald Joyce (pictured above) and his colleague Tracey Lincoln have built an “immortal molecule.”  They have synthesized RNA enzymes – ribonucleic acid enzymes also known as ribozymes – that replicate themselves without the help of any proteins or other cellular components.  And since these simple nucleic acids can act as catalysts, the process can continue indefinitely.

As Cosmos reports,

The ultimate goal is to create genetic systems that behave like life, and are for all intents “life” as we know it, but arose without using biological systems.

“The aim is to create systems that have inventive capabilities, that can develop novel solutions to challenges posed by the environment. But that we don’t have yet,” [Joyce] said.

“What we do have is a self-sustained chemical system that undergoes Darwinian evolution. They are synthetic genetic systems, and they are evolving. But they’re not living because they don’t yet show the capacity to invent a whole cloth of functions. The idea is to give them enough information wherewithal [genetic building blocks] so they can start inventing their own solutions rather than just optimizing existing solutions,” he added.

Joyce said it was not practical to synthesize the more complex DNA-based life we know from scratch; it’s too complex and probably beyond today’s science. But it is conceivable to start with a much more basic form of life-like molecules based on RNA, and use evolution to build on them.

Many scientists believe that early life was based on RNA and predated the arrival of life based on deoxyribonucleic acid (DNA) and proteins. RNA, which can both store information like DNA as well as act as an enzyme like proteins, may have supported pre-cellular life.

A leading proponent of this so-called “RNA world” hypothesis, Joyce believes that RNA-based catalysis and information storage may have been the first step in the evolution of cellular life.

Read the whole story here.

As we search our closets for those chemistry sets, we might celebrate the emergence of a technology that took on a life of its own and changed… well, everything:  this date in 1455 is the traditionally-given date of the publication of the Gutenberg Bible, the first Western book printed from movable type.  The Jikji— the world’s oldest known extant movable metal type printed book– was published in Korea in 1377.  Bi Sheng created the first known moveable type– out of wood– in China in 1040.

The Library of Congress’ copy

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