(OLD VIDEO) Protein Synthesis and the Lean, Mean Ribosome Machines


Captioning is on. To turn off, click the CC button at bottom right. Follow us on Twitter @amoebasisters and Facebook! Lately, we have been talking about DNA, and
how AWESOME DNA is. But what we have not talked about is how DNA actually codes for your traits.
Say, for example, we’re talking about your eye color. Yes, the DNA codes for the genetic
information that codes for the color of your eyes. How exactly does that work? Well, keep
in mind that your eyes are the color that they are based on a pigment that is inside
the eyes. In order to have that pigment, your DNA must code for proteins that help make
that pigment, which gives them their color. So today what we’re going to talk about
is how your DNA leads to a protein. This is actually called protein synthesis. Just like
it sounds -whenever you say synthesis – that means to “make something.” Protein synthesis
means to make protein. Whenever we’re talking about protein synthesis, we also need to realize
this is happening in all of your cells. All of your cells contain your DNA. While not
all of the DNA is turned on at any given time (it’s based on what kind of cell we’re
talking about), that DNA is present in the nucleus of all of your cells. What we have
to consider is, “How are we going to get the genetic information that’s in the DNA (which
is inside the nucleus) out of the nucleus so that the cell can start producing the proteins
that it needs to make based on the genetic instructions?” Well in order to answer that
question, we need to go into the process of protein synthesis. In protein synthesis, there
are two major steps. One is transcription and the other is translation. There are actually
a lot of “trans” words that we’ll get into in biology, but just stay with me here.
Transcription has a C in it, and translation has an L in it. I remember that C comes before
L in the alphabet, which helps me remember that transcription comes first. That’s always
kind of helped me. Now, transcription is when we’re going to transcribe the DNA into a message.
If you think about that, think where DNA is. The DNA is always in the nucleus, so we’re
starting transcription in the nucleus. The DNA is going to have matching RNA bases matched
up to it with the help of enzymes to make mRNA. In transcription, we make mRNA. We made
a message out of RNA. At the end of transcription, we have made an mRNA molecule. Remember that’s
messenger RNA. One great thing about being an mRNA? You can get out of the nucleus. The
mRNA goes out of the nucleus where it’s going to attach to a ribosome. Remember, ribosomes
make protein. Also remember that the r for ribosomal RNA is what makes up a ribosome.
The messenger RNA is going to go to a ribosome, which is made out of rRNA, and use the message
to build our protein. This step is going to be called translation because we’re translating
our message into protein. We are also outside of the nucleus, we are in a ribosome so that
is our location is now. You know, you can find a lot of great clips and animations on
translation that are just fantastic. What I like to think of you’ve got this mRNA
and it’s in a ribosome and then you have these tRNAs coming in. tRNA, remember
that stands for transfer RNA, they have an amino acid on them. An amino acid is the monomer
for a protein; it is a building block for protein. If you get a bunch of amino acids
together, you build this big ole protein. All of these tRNAs are looking for the matching
bases on the mRNA. When they find the matching base pairs on the mRNA, they carry and drop off
their amino acids that it goes to. So eventually what ends up happening is you get this big
chain of amino acids that have to match up with the coding on the mRNA. The different
amino acids are held together by a peptide bond, which is basically a protein bond. You
end up with a really long protein made of all these amino acids, which now can be used
for all kinds of different body processes and that could be something, for example,
if we’re going to make eye pigment. One important thing to mention is that when the
tRNA is bringing in the amino acids, it reads the letters on the mRNA in threes. This means
that every time you have three bases, that is how it reads it. So it doesn’t read one
letter at a time, it reads it in triplets. That’s called a codon. A codon is three
bases. So, for example, if you had an mRNA strand, you wouldn’t just read: A,
then U, then G, then some other letter. It would read AUG together in a triplet, a codon.
Because it reads in threes, when we get into mutations we’ll talk about how if you end
up taking out one letter it could be very bad. If you read in threes and you take out
one letter, it will mess up your reading frame for the rest of that strand. When we get into
mutations, we’ll really get into that. One thing I really like to encourage with topics
like this in biology, it’s really great to have some kind of activity so that you
can really walk through it. It’s really hard to visualize this protein synthesis,
but if you can do an activity where you’re actually involved in it, it can help make
a lot more sense, I promise. So if you do a search for “PBS DNA Workshop,”
you will pull this great resource. The PBS DNA Workshop not only has a little workshop
of DNA replication, but it also has a great protein synthesis activity where it will actually
let you do the protein synthesis – both the transcription and translation. It’s
highly recommended. Anyway, that’s it for the Amoeba Sisters, and we remind you to stay
curious. Follow us on Twitter @amoebasisters and Facebook!