Kind: captions
Language: en
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if you could step inside one of your
cells you'd see something that looks a
lot like a factory building thousands of
different molecular machines it would
have tiny assembly lines starting in the
cell's nucleus and stretching out to
structures called
ribosomes these assembly lines start
with DNA and build rnas and proteins in
a very real sense you DNA has all the
blueprint for everything the cell will
ever need to build rnas are assorted
molecular machines that do all kinds of
work in the cell they carry components
from place to place ratchet up the speed
of operations switch other machines on
and off and relay coded instructions
from the nucleus out to the factory
floor the other product proteins are
strong molecular machines that do things
like hold the cell together and send
signals to other
cells there are two parts to each
assembly line the first builds rnas and
the second builds
proteins the process that builds rnas is
called
transcription it happens in the cell's
central office the nucleus where DNA
blueprints are stored let's say that a
cell needs to make a transfer RNA or
TRNA a triangle-shaped RNA which
transports a building material called an
amino acid it starts at a tiny specific
region of DNA with the code that makes
the TRNA we need this region is called a
gene
a protein machine inside the nucleus PR
apart the weak bonds that hold the two
strands of DNA together RNA building
blocks swarm in and form a congol line
complimentary to the
DNA this RNA strand now needs to fold up
in the world of tiny cellular machines
shape determines function rna's four
bases bond to each other and give the
TRNA its 3D shape and voila our Transfer
RNA is ready for action it floats out of
the nucleus and picks up an amino acid
we'll come back to our TRNA in just a
moment now let's look at the second half
of the factories assembly line making
proteins from RNA a process called
translation remember the scrape this
cell needs to make thrombin a protein
machine which helps blood clot and make
a scab thrombin is just one of the tens
of thousands of proteins your cells can
make before translation Begins the cell
transcribes a special type of RNA called
m RNA or messenger RNA this mRNA carries
the code for thrombin out of the nucleus
and onto the cellular Factory
floor our mRNA drifts until it runs into
a ribosome a protein making machine the
ribosome clamps down around the MRNA
trnas just like the one we made earlier
drift in the messenger RNA carries a
coded message which the trnas translate
into amino acids the language of
proteins this process translation
proceed Leeds down the MRNA creating a
chain of bonded amino acids just as with
RNA molecular shape determines molecular
function so these amino acids fold up
into the protein's three-dimensional
form finally the ribosome comes to a bit
of code that says okay we're done here
and releases its completed protein into
the
cell so there you have it DNA encodes
genes to make RNA machines and the
ribosome translates special mRNA which
in turn makes protein
machines unlike most factories your cell
uses just two processes to make tens of
thousands of different molecular
machines it's like one Factory that can
build toasters phones cars and even
repair itself
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