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Course: NOVA Labs > Unit 1
Lesson 3: RNA: the wonder molecule- The RNA enigma
- The RNA engima quiz
- RNA: The basics
- Protein synthesis in the cellular factory
- Protein synthesis in the cellular factory quiz
- Protein synthesis
- The RNA origin of life
- The RNA origin of life quiz
- RNA world
- Virus wars
- Virus wars quiz
- Viruses
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Protein synthesis in the cellular factory
RNA may have been the origin of life on Earth. Go on a whirlwind tour of RNA’s evolving role through billions of years of evolutionary history. Created by NOVA.
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- Where do the messenger rna's go after they finish transferring the message? Do they just float around?(15 votes)
- RNAs are not very stable. The mRNAs generally do not "live" much longer than a few minutes, then they are destroyed by Enzymes called RNAses, of which every cell has lots and lots.(13 votes)
- What would happen if Thrombin had never been created during translation?(3 votes)
- Are errors in the transcription or translation processes in protein synthesis the cause of tumors/ cancer?(3 votes)
- Partially. These are called nucleotide mutations. The mutations need to occur in specific regions for the mutations to have negative side effects. This is because more than half of our DNA is made up of odd sequences whose function is unknown. These sequences include codons, histones, etc.(7 votes)
- Are there many of these factories?(3 votes)
- I think they were referring factories to cells, using it as a metaphor.(3 votes)
- So are organelles the same things as proteins?(3 votes)
- No. Organelles are structures with a specific function in cells, proteins send messages and are made up of amino acids.(3 votes)
- What happens to the mRNA after being translated by the Ribosome?(3 votes)
- RNA is very unstable, and after they've outlived their usefulness, enzymes break down the RNA so there isn't clutter in and around the cell.(3 votes)
- How do different RNA shapes perform different functions? Do they just use the most efficient shape possible for the job that they need to do?(3 votes)
- How does a cell know to start protein synthesis?(3 votes)
- Do two ribosomes come together during the translation process?(2 votes)
- No. The two parts that you see are actually subunits of ONE ribosome.(2 votes)
- Can the nucleus instruct to create white cells?(2 votes)
Video transcript
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 blueprints 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 pries
apart the weak bonds that hold the two strands of DNA together. RNA building blocks swarm
in and form a conga line complementary 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 factory's
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 mRNA, 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, proceeds 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 3 dimensional form. Finally, the ribosome comes to a bit of code
that says "ok, 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.