Protein Synthesis (Part 2 of 2) - Translation
Summary
TLDRThis script from a protein synthesis video series explains the process of translation, where mRNA moves from the nucleus to the cytoplasm and is translated into proteins at the ribosome. Using plasticine balls to represent amino acids, the video illustrates how codons on mRNA are matched by transfer RNA's anticodons to build a polypeptide chain. It emphasizes the importance of the amino acid sequence in determining a protein's structure and function, concluding with a diagram showing the journey from DNA to a functional protein.
Takeaways
- 🔬 Translation is the process where mRNA is translated into a protein, occurring after transcription.
- 🧬 The mRNA is formed in the nucleus during transcription and then moves to the cytoplasm for translation.
- 🧫 Translation takes place at the ribosome, which is often located on the rough endoplasmic reticulum.
- 🔡 The sequence of mRNA bases (codons) determines the sequence of amino acids in the protein.
- ⚗️ Transfer RNA (tRNA) is responsible for bringing the correct amino acid to the ribosome, matching its anticodon with the mRNA codon.
- 🔗 A polypeptide chain is formed as amino acids are added sequentially, with each tRNA bringing a new amino acid to the chain.
- 🧩 The sequence of amino acids in a polypeptide chain determines the protein's final structure and function.
- 🚦 Translation continues until a stop codon is reached, at which point the polypeptide is released and folds into its three-dimensional structure.
- 🏗️ The tertiary structure of a protein is crucial for its functionality, and any changes in the sequence can affect its function.
- 📜 Overall, the sequence of nucleotides in the DNA determines the sequence of amino acids and the structure of proteins produced in cells.
Q & A
What is the main focus of this video in the protein synthesis series?
-The main focus of this video is translation, which is the process where the messenger RNA (mRNA) is translated into a protein.
What is the difference between transcription and translation?
-Transcription is the process where DNA is transcribed into mRNA in the nucleus, whereas translation is the process where the mRNA is translated into a protein in the cytoplasm at the ribosome.
What role do ribosomes play in protein synthesis?
-Ribosomes serve as the site where translation occurs. They facilitate the interaction between mRNA and transfer RNA (tRNA) to assemble amino acids into a polypeptide chain, forming a protein.
What is the function of transfer RNA (tRNA) in translation?
-tRNA's function is to transfer specific amino acids to the ribosome during protein synthesis. It carries the amino acid to the ribosome and matches its anticodon with the codon on the mRNA to add the correct amino acid to the growing polypeptide chain.
What are codons and anticodons?
-Codons are sequences of three nucleotide bases on the mRNA that code for specific amino acids. Anticodons are complementary sequences of three bases on the tRNA that pair with the codons on the mRNA, ensuring that the correct amino acid is added to the growing polypeptide chain.
Why is the sequence of amino acids important in proteins?
-The sequence of amino acids determines the final structure of the protein, which is crucial for its function. If the sequence is altered, the protein may not fold correctly, leading to a loss or change in function.
What is a start codon, and what role does it play in translation?
-A start codon is a specific sequence of three nucleotide bases (AUG) on the mRNA that signals the start of protein synthesis. It also codes for the amino acid methionine, which is the first amino acid in the newly synthesized protein chain.
How does the process of translation terminate?
-Translation terminates when the ribosome encounters a stop codon on the mRNA. Stop codons do not code for any amino acid, signaling the end of the polypeptide chain, causing it to be released and the protein synthesis to complete.
What happens to the polypeptide chain after translation is complete?
-After translation, the polypeptide chain detaches from the ribosome and folds into its three-dimensional structure, forming a functional protein. This folding is essential for the protein to carry out its specific function in the cell.
How does the genetic code ensure that proteins are synthesized correctly?
-The genetic code ensures accurate protein synthesis by having a specific codon for each of the 20 amino acids. The tRNA molecules with complementary anticodons bring the correct amino acids to the ribosome, ensuring that the amino acid sequence matches the sequence encoded by the mRNA, which was transcribed from the DNA.
Outlines
🔬 Understanding Translation in Protein Synthesis
This paragraph introduces the second part of a video series on protein synthesis, focusing on the process of translation. It briefly recaps the first part, which covered transcription—the process where DNA in the nucleus is transcribed into messenger RNA (mRNA). The paragraph then transitions to the current focus: how mRNA moves to the cytoplasm and is translated into a protein. The speaker uses plasticine balls as a visual aid to represent amino acids and explains their role in forming proteins. The process of translation involves decoding the sequence of bases in mRNA (represented by letters U, A, C, and G) into a sequence of amino acids to form a protein. The importance of the sequence of amino acids, which determines the protein's final structure and function, is also emphasized.
🔗 Role of Transfer RNA in Protein Formation
This paragraph delves into the function of transfer RNA (tRNA) in the translation process of protein synthesis. It explains how tRNA molecules transfer specific amino acids to the growing polypeptide chain at the ribosome. Each tRNA has an anticodon that is complementary to an mRNA codon, ensuring that the correct amino acid is added according to the mRNA sequence. The paragraph describes the movement of tRNA and mRNA through the ribosome, detailing how tRNA releases its amino acid and is recycled for further use. The step-by-step elongation of the polypeptide chain through the addition of amino acids, guided by the mRNA sequence, is also covered.
🧬 Folding of Polypeptides into Functional Proteins
This paragraph discusses the final stages of protein synthesis, where the polypeptide chain folds into its three-dimensional structure after being released from the ribosome. It emphasizes that this tertiary structure is crucial for the protein's function. A diagram is referenced to illustrate the complexity of the three-dimensional structure. The paragraph also reviews the entire protein synthesis process from DNA to protein, highlighting how the sequence of nucleotides in DNA ultimately determines the sequence of amino acids in a protein, thus influencing the protein's structure and function. The video concludes with an invitation for questions and a light-hearted comment about a pop quiz.
Mindmap
Keywords
💡Translation
💡mRNA (messenger RNA)
💡Ribosome
💡Codon
💡tRNA (transfer RNA)
💡Amino Acid
💡Polypeptide Chain
💡Anticodon
💡Start Codon
💡Stop Codon
Highlights
Introduction to the second part of the protein synthesis video series focusing on the process of translation.
Explanation of the transcription process from the first video, where DNA is transcribed into mRNA.
Use of plasticine balls to represent amino acids in the translation process.
Description of how mRNA moves from the nucleus to the cytoplasm for translation.
The role of ribosomes in the translation process and their location on the rough endoplasmic reticulum.
Explanation of the start codon (AUG) and its significance in identifying the beginning of a gene.
Introduction of transfer RNA (tRNA) and its function in transporting amino acids to the ribosome.
The concept of codons and anticodons in matching tRNA to the correct amino acid.
Demonstration of how the first amino acid, methionine, is brought to the ribosome by tRNA.
Process of polypeptide chain formation, with amino acids being added one by one.
The role of different tRNAs in collecting specific amino acids based on the mRNA codon.
Illustration of the polypeptide chain growth and the detachment of used tRNAs.
The importance of the correct amino acid sequence for the protein's final structure and function.
The continuation of the translation process until a stop codon is reached.
Description of the polypeptide folding into its three-dimensional structure after translation.
Final diagram summarizing the process from DNA to protein synthesis.
Emphasis on the critical role of DNA sequence in determining amino acid sequence and protein structure.
Conclusion of the protein synthesis video series and invitation for questions.
Transcripts
so this is the second and final part of
the protein synthesis video series this
video is about a process called
translation in part one and if you
haven't checked it out yet go and have a
look we looked at
transcription which is the process where
the DNA in the nucleus is transcribed at
the location of the gene into some
messenger RNA or mRNA so let's have a
look at how that mRNA then moves out
into the cytoplasm and is
translated into a
protein
awesome woof
woof oh
oh uh sorry about
that okay uh so you're probably
wondering what on Earth I'm doing with
these plasticine balls well they have a
role to play hopefully they're going to
help me to explain translation to you
let me
explain so in part one when we were
talking about transcription we were
looking at how we read the code on the
DNA the Gene and make make our messenger
RNA or
mRNA in part two as I've said we're
going to be looking at how do we
translate the message on that RNA which
is in the form of u a c and G those four
nucleotide bases how do we get from the
sequence of bases to a sequence of amino
acids which is what form a protein and
yep you guessed it that's what my little
plasticine balls are here they represent
our amino acids we know there are 20
different types I didn't have 20
different colors unfortunately so I'm
just representing a few of our amino
acids here and we're going to have a
look at how a cell reads the code on
that RNA and then translates it into a
sequence of amino acids to form a
protein as you can see the amino acids
are all different and it's the sequence
of those Amino acids that is critical to
the final structure of a protein and
therefore the way that it
functions so the process of translation
takes place out in the
cytoplasm at the
ribosome and you may or may not know but
ribosomes are commonly located on the
rough endoplasmic reticulum so here we
have a ribosome there quite simple made
of two subunits a bigger subunit and a
smaller subunit at the ribosome our
messenger RNA will
arrive so here's some messenger RNA like
the messenger RNA that was transcribed
in video one it's not exactly the same
strand of messenger RNA it's got a
slightly different Bay sequence but it
does begin with a
u that's important because a ug is the
start code on and that is how the cell
knows where a gene starts there's also a
stop code on and we'll talk about that a
bit later so our messenger RNA is going
to arrive at the
ribosome and it sits in between the two
subunits something a little like that
now there's another couple of components
that we need to bring in some of those
are our amino acids so here we have a
selection of amino acids represented by
some different colors and different
shapes remember there are 20 so we
haven't got all of the different types
of amino acids there but we've got a
selection and somehow as we've said
those amino acids need to be placed into
position in the correct sequence to form
the correct protein and we know that
every three bases on the MRNA is called
a codon and codes for one amino acid for
example
Aug which as I just explained before and
I'll just bring in our genetic code here
Aug is the start codeon it also codes
for the amino acid
methionine so here's methine up
here how is this amino acid going to
find its way down to the corresponding
codon and begin a polypeptide chain and
start the process of this protein
forming well what's involved is a
molecule that helps to transfer the
amino acid to the
chain this is what we call transfer RNA
it is an RNA
Strand and we call it Transfer RNA
because obviously its job is to transfer
an amino acid now the way Transfer RNA
molecules or tRNA molecules recognize
and know which amino acid to place in
the chain at which particular location
is due to this base triplet here which
is complementary to the codon and
therefore we call it an anticodon and if
the anti-codon matches up with the codon
then it will place the Amo acid in the
chain so the TRNA will collect the
appropriate amino acid and then it will
transfer the amino acid to the ribosome
ready to start this polypeptide chain
forming now one of the things you would
have picked up on TRNA still has the
base U and not the base T and of course
that's because it is RNA and not
DNA now next we have a codon of a a g c
let's bring in our genetic code again
AGC is over here and it codes for seene
the amino acid seene so
AGC what will our antic code on be on
the TRNA molecule it should be U
CG and here is that transfer RNA
molecule it's going to collect a Serene
amino acid and transfer the cine amino
acid to the ribosome so that it combined
with the first amino acid and start our
polypeptide chain the next thing that
happens as you can see everything's
moved along one and the the transfer RNA
that dropped off methionine that can
then detach move away from the ribosome
and it can go and transfer another
methionine into the growing polypeptide
chain and the other thing that you can
see that's happened the bond has formed
between the first and second amino acid
so next we have
ccg
ccg is the codon for the amino acid
Proline the transfer RNA with the
anticodon that is complementary to that
codon is
GGC that's going to collect a proline
amino
acid and transfer it down to the
ribosome and then again everything
shifts along
one and so here you have it everything's
moved along one a bond has formed
between the cerine and proline amino
acids and then the next Transfer RNA is
going to come in this time UAC means
it's going to collect a tyrosine amino
acid transfer tyrosine down to the
ribosome and the process continues so
our polypeptide chains really growing
here next Transfer RNA comes in
auu is the corresponding code on for
isoline so isoline will be collected by
the transfer RNA delivered to the
ribosome process
continues
AGC we've had that one before over here
that coded for cine so of course another
serine amino acid
will be collected by the transfer RNA
and delivered to the ribosome and the
last one I've got here is
agu
agu actually codes for cine as well
because remember in some cases there is
more than one codon for a particular
amino acid so a transfer RNA with the
anticodon for agu of UCA will collect
the cine amino acid and bring it to the
ribosome so what we've been seeing here
is the polypeptide chain of amino acids
gradually growing by one amino acid at a
time of course this process happens a
lot faster inside of cells and this of
course is not finished yet genes in
reality are much much longer I've only
just shown you a small segment so that
you can get an idea of what's happening
this will keep on continuing until a
stop code on reached when a stop codon
is reached the polypeptide molecule will
detach from the
ribosome and it will fold up into its
three-dimensional structure which is
hard to show or demonstrate with these
paper cutouts but I've got a diagram
here which might give you a bit of a
better idea this is a three-dimensional
protein structure also referred to as
its tertiary structure and as we know
really well it's the overall structure
of a protein that is absolutely critical
to its function if the protein doesn't
have this exact structure it won't be
able to function
correctly so there you have it that's
protein synthesis we've now been through
transcription and translation we've seen
how we can get from DNA to an eventual
protein I've got a final diagram here to
help bring all bring it all into
perspective we've got the DNA which is
of course inside of the nucleus this is
our nuclear membrane in transcription
which happens in the nucleus the DNA
separates at the location of the gene
messenger RNA is formed in a
complimentary manner to the gene that
messenger RNA then mve moves out through
the nuclear pore to the ribosome in the
cytoplasm it's then
translated by a process where Transfer
RNA molecules collect the specific amino
acid and place it in the growing
polypeptide chain according to the base
sequence on the messenger RNA remember
the most important point is that the
messenger RNA was
synthesized using the DNA or the gene as
a template so what you can see in this
overall diagram is that it's the
sequence of nucleotides in the DNA that
determines the overall sequence of amino
acids and therefore structure of the
proteins produced in cells guys that's
been protein synthesis it's been an
absolute pleasure thanks very much for
watching and I'll see you next time any
questions before free time yeah didn't
you there was going to be a pot quiz
today what was that Thomas I didn't say
nothing I didn't say anything
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