Protein Synthesis (Part 2 of 2) - Translation

Summary

This 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

00:00

🔬 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.

05:02

🔗 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.

10:06

🧬 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.

Keywords

💡Translation

Translation is the process by which messenger RNA (mRNA) is decoded to produce a specific sequence of amino acids, which form a protein. This is a key step in protein synthesis, occurring in the cytoplasm at the ribosome. The video explains how the sequence of bases in mRNA is read to produce the corresponding amino acid chain.

💡mRNA (messenger RNA)

mRNA is a type of RNA that carries the genetic information from DNA to the ribosome, where it is used as a template for protein synthesis. In the video, mRNA is described as the molecule that is transcribed from DNA and then transported to the cytoplasm to be translated into a protein.

💡Ribosome

A ribosome is a cellular structure where protein synthesis takes place. It reads the mRNA sequence and assembles amino acids into a polypeptide chain. The video describes ribosomes as being composed of two subunits and explains how they facilitate the translation of mRNA into protein.

💡Codon

A codon is a sequence of three nucleotide bases in mRNA that corresponds to a specific amino acid. The video explains that codons are essential for determining the order of amino acids in a protein, and the AUG codon is highlighted as the start codon.

💡tRNA (transfer RNA)

tRNA is a type of RNA that carries amino acids to the ribosome during translation. It matches its anticodon with the corresponding codon on the mRNA, ensuring that the correct amino acid is added to the growing polypeptide chain. The video shows how tRNA is crucial for translating the genetic code into a protein.

💡Amino Acid

Amino acids are the building blocks of proteins. There are 20 different types, each represented by a specific codon in mRNA. The video uses colored plasticine balls to represent amino acids and explains how they are assembled into a polypeptide chain based on the mRNA sequence.

💡Polypeptide Chain

A polypeptide chain is a sequence of amino acids linked together, forming the basic structure of a protein. The video demonstrates how amino acids are added one by one to a growing polypeptide chain during translation.

💡Anticodon

An anticodon is a sequence of three bases on tRNA that is complementary to a codon on mRNA. It ensures that the correct amino acid is added to the polypeptide chain. The video explains how anticodons allow tRNA to deliver the right amino acid based on the mRNA sequence.

💡Start Codon

The start codon, usually AUG, signals the beginning of protein synthesis. It also codes for the amino acid methionine. The video mentions the start codon as the point where translation begins, marking the start of the gene being translated into protein.

💡Stop Codon

A stop codon signals the end of protein synthesis, causing the ribosome to release the completed polypeptide chain. The video references stop codons as the point where the translation process concludes and the newly formed protein detaches from the ribosome.

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