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Living things often have workers wandering around trying their
Instructions on everything
they bump into, but there are some jobs that require better
organization. For instance, Life's process for extracting energy from
sugar requires at least ten steps, each a chemical change. If living
things couldn't do this quickly and efficiently, they'd starve. To
carry out complex tasks with many steps, living things organize the
workers which carry out those steps into clusters called
complexes. Each cluster is something like an assembly line in
a real factory, with the difference that there is no conveyer belt.
Instead, workers pass materials back and forth among
themselves. Workers that are in complexes usually have an Instruction
that includes holding onto one or more of the other workers in the
complex. Sometimes, the complex contains special workers whose
Instruction is to hold the complex together.
The set of steps needed to carry out a series of chemical changes is called
a pathway. For instance, the ten steps for getting energy from sugar
are called the glycolytic ("sugar-cutting") pathway.
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changing ethyl alcohol to acetaldehyde and then acetic acid
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The shortest pathways have only two steps. One of
these very short pathways is the pathway the human body uses to
detoxify alcohol -- specifically, the ethyl alcohol in beer,
wine, and other drinks. In the first step of this pathway, a worker
called alcohol dehydrogenase I snips two hydrogen
atoms off of
every molecule of ethyl alcohol it runs into, turning it into
acetaldehyde. Acetaldehyde is actually much more toxic than
ethyl alcohol, but another worker (aldehyde dehydrogenase I)
replaces another of its hydrogen atoms with an oxygen atom and a
hydrogen atom, turning it into acetic acid. Acetic acid is the
acid in vinegar, and isn't harmful to us (in small quantities).
Living things have other tricks for making things more efficient in
their factories. Nearly all factories have an internal railroad
system, the individual lines of which are called micro-tubules.
The whole system is made of workers: the rails are workers, as are the
cars and locomotives. Eukaryotes
also have many rooms in their factories, each dedicated to a specific
function. These rooms are called organelles.
So far, we've discussed what workers do without saying what the
sum of all the work adds up to: visible effects on the living thing
the workers make up. Or, in other words, how do we see the effects
of workers which are themselves too small to be seen?
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We'll be seeing a lot of alcohol dehydrogenase I in this site. Al
(as he's known to friends) is a typical worker, and unlike most workers in
living things, directly produces a familiar effect.
more about Al
Curious readers may wonder where the hydrogen atoms Al snips off go. Al
pastes one onto another molecule called NAD, whose purpose is to
carry around hydrogen atoms. The other floats off by itself.
Al moving hydrogen atoms
Here's Aldehyde Dehydrogenase, the other half of the team:
more about Aldehyde
Dehydrogenase
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