Protein Synthesis (Updated)

Summary

This video script from Amoeba Sisters dives into the fascinating process of protein synthesis, starting from DNA and involving RNA. It explains how genes in DNA are transcribed into mRNA, which then translates into proteins with the help of tRNA and rRNA. The script simplifies complex biological processes, highlighting the importance of proteins in various cellular functions and using a codon chart to illustrate how amino acids are assembled into proteins based on mRNA codons.

Takeaways

• 🧬 DNA contains genetic information that codes for traits like eye color.
• 👁️ Eye color is determined by pigments produced through proteins coded by genes.
• 🧪 Protein synthesis involves creating proteins essential for various bodily functions.
• 🏗️ Proteins play crucial roles in transport, structure, enzymes, and protection.
• 🔬 Protein synthesis occurs in two major steps: transcription and translation.
• 🧾 Transcription involves transcribing DNA into mRNA in the nucleus.
• 💌 mRNA carries the genetic message from DNA to the cytoplasm.
• 🏭 Translation happens in the ribosome where mRNA is used to assemble proteins.
• 🔗 tRNA brings amino acids to the ribosome based on mRNA codons.
• 📊 A codon chart helps determine which amino acids correspond to specific mRNA codons.
• ⛓️ Amino acids are linked by peptide bonds to form proteins, directed by mRNA sequences.
• 🛑 The process ends when the ribosome reaches a stop codon, completing the protein chain.

Q & A

What is the main topic discussed in the video script?

The main topic discussed in the video script is the process of protein synthesis, specifically how DNA results in a trait through the creation of proteins.

Why is the pigment inside the eyes important for determining eye color?

The pigment inside the eyes is important for determining eye color because it is the substance that reflects the light, giving the eyes their color. Genes code for proteins that help make this pigment.

What does the term 'protein synthesis' mean?

Protein synthesis refers to the process by which cells create proteins, which are essential for various functions including transport, structure, enzyme activity, and protection of the body.

What is the role of RNA in protein synthesis?

RNA plays a crucial role in protein synthesis by transcribing the DNA into a message (mRNA) and then translating this message into a sequence of amino acids to build a protein.

What are the two major steps in protein synthesis?

The two major steps in protein synthesis are transcription and translation. Transcription is the process of creating mRNA from DNA, and translation is the process of using this mRNA to build a protein.

What is the purpose of RNA polymerase in the transcription process?

RNA polymerase is an enzyme that connects complementary RNA bases to the DNA during transcription, forming a single-stranded mRNA that carries the genetic message for protein synthesis.

What is the significance of mRNA editing mentioned in the script?

mRNA editing is significant because it refines the mRNA before it is used in translation, ensuring that the genetic message is accurate and can be correctly translated into a functional protein.

What is the role of tRNA in the translation process?

tRNA (transfer RNA) carries specific amino acids to the ribosome during translation. Each tRNA has an anticodon that is complementary to an mRNA codon, ensuring that the correct amino acid is added to the growing protein chain.

What is a codon and why is it important in translation?

A codon is a sequence of three mRNA bases that codes for a specific amino acid. It is important in translation because it determines the sequence in which amino acids are added to the protein being synthesized.

What is the function of a start codon in protein synthesis?

A start codon, such as AUG, signals the beginning of translation. It is where the ribosome starts to read the mRNA and where the synthesis of the protein begins, typically with the amino acid methionine.

What are stop codons and their role in translation?

Stop codons are special codons that do not code for any amino acid. They signal the ribosome that the protein synthesis is complete, and no more amino acids should be added to the protein chain.

How does the process of protein synthesis relate to the traits we exhibit, such as eye color?

Protein synthesis is the process by which the information in our DNA is used to create proteins that contribute to our traits. For example, the proteins involved in the production of pigments in the eyes determine our eye color.

Outlines

00:00

🧬 DNA and Protein Synthesis Introduction

This paragraph introduces the concept of protein synthesis, which is the process by which DNA leads to the creation of proteins. It explains that DNA contains genetic information that codes for various traits, such as eye color, through the production of pigments. The paragraph emphasizes the importance of proteins in the body, which are involved in numerous functions including transport, structure, enzymatic reactions, and protection. It also introduces the two major steps in protein synthesis: transcription and translation, with a brief mention of RNA's role in this process. The script acknowledges the simplification of a complex topic and encourages further exploration for a deeper understanding.

05:00

📜 The Mechanism of Transcription and Translation

This paragraph delves into the specifics of transcription and translation within the cell. Transcription is described as the process where DNA is transcribed into mRNA by the enzyme RNA polymerase within the nucleus. It highlights the editing that occurs to mRNA before it leaves the nucleus and enters the cytoplasm. The paragraph then explains translation as the process where mRNA attaches to a ribosome, which is composed of rRNA, to begin protein synthesis. The role of tRNA (transfer RNA) is detailed, including how it carries amino acids to the ribosome based on the codons present on the mRNA. The use of a codon chart to match mRNA codons to their corresponding amino acids is introduced, and the concept of start and stop codons is explained. The paragraph concludes by discussing how the resulting chain of amino acids forms a protein, which may undergo further folding and modification before performing its function in the cell.

Keywords

💡DNA

DNA, or Deoxyribonucleic Acid, is a molecule that carries the genetic instructions for the development, functioning, growth, and reproduction of all known living organisms and many viruses. In the context of the video, DNA is highlighted as the starting point for the process of protein synthesis, with specific genes within the DNA coding for proteins that determine traits such as eye color.

💡Pigment

A pigment is a colored substance that is used for coloring any material. In the video, pigment is mentioned as the substance within the eyes that determines eye color. The presence and type of pigment are influenced by the proteins encoded by genes in an individual's DNA.

💡Protein Synthesis

Protein synthesis is the process by which cells generate new proteins. It is central to the video's theme, illustrating how DNA leads to the creation of proteins, which are essential for the structure, function, and regulation of the body's tissues and organs.

💡Proteins

Proteins are large biomolecules composed of one or more long chains of amino acid residues. They are crucial for the proper functioning of the body, playing roles in transport, structure, enzymatic reactions, and immune response. The video emphasizes the importance of proteins and the ongoing process of protein synthesis within the body.

💡Nucleus

The nucleus is a membrane-bound organelle found in eukaryotic cells that contains the cell's genetic material. In the video, the nucleus is identified as the location within the cell where DNA is stored and where the process of transcription begins.

💡RNA

RNA, or Ribonucleic Acid, is a nucleic acid that is similar to DNA but has a few key differences. In the context of protein synthesis, RNA plays a critical role in transcribing the genetic information from DNA and translating it into a sequence of amino acids to build proteins.

💡Transcription

Transcription is the first major step in protein synthesis where the genetic information from DNA is copied into a molecule of messenger RNA (mRNA). The video explains that this process occurs in the nucleus and is facilitated by the enzyme RNA polymerase.

💡mRNA

mRNA, or messenger RNA, is a single-stranded RNA molecule that carries the genetic information from DNA to the ribosome, where it serves as a template for protein synthesis. The video describes how mRNA is created during transcription and edited before it leaves the nucleus.

💡Ribosome

A ribosome is a complex molecular machine found within cells that synthesizes proteins from amino acids. In the video, ribosomes are depicted as the site where translation occurs, using mRNA as a template to build proteins.

💡tRNA

tRNA, or transfer RNA, is a type of RNA that carries a specific amino acid to the ribosome during protein synthesis. The video explains how tRNA molecules, through their anticodons, recognize and bind to the codons on the mRNA, ensuring the correct sequence of amino acids in the growing protein chain.

💡Codon

A codon is a sequence of three nucleotides on mRNA that specifies a particular amino acid. The video describes how codons are read by tRNAs in groups of three during translation, with each codon corresponding to a specific amino acid.

💡Peptide Bond

A peptide bond is a chemical bond that links two amino acids together in a protein. The video mentions peptide bonds as the linkage that forms between amino acids as they are brought together by tRNAs during translation, creating the protein chain.

💡Stop Codon

A stop codon is a sequence of three nucleotides on mRNA that does not code for an amino acid but instead signals the end of protein synthesis. The video explains that when the ribosome encounters a stop codon during translation, it ceases the addition of further amino acids, completing the protein synthesis process.

Highlights

DNA contains genetic information that determines eye color through the production of pigments.

Protein synthesis is the process by which DNA leads to the creation of proteins, which are essential for life.

Proteins have various functions including transport, structure, enzyme activity, and body protection.

All human cells contain DNA, with some being noncoding or genes that are not activated.

RNA plays a crucial role in protein synthesis, being a nucleic acid with differences from DNA.

Protein synthesis involves two major steps: transcription and translation.

Transcription is the process of copying DNA into a messenger RNA (mRNA) within the nucleus.

RNA polymerase is the enzyme responsible for transcribing DNA into mRNA.

mRNA undergoes editing before it can be used in protein synthesis.

In eukaryotes, mRNA exits the nucleus to be translated in the cytoplasm.

Ribosomes, made of rRNA, are the cellular structures responsible for protein synthesis.

Transfer RNA (tRNA) carries amino acids, the building blocks of proteins, to the ribosome.

tRNA uses its anticodon to find complementary bases on mRNA, determining which amino acid to add.

Codons are triplets of mRNA bases that specify a particular amino acid.

AUG is a start codon that codes for methionine, typically the first amino acid in a protein.

Multiple codons can code for the same amino acid, such as the codons for leucine.

A stop codon signals the end of protein synthesis, with no corresponding amino acid.

The final protein structure is determined by the sequence of amino acids coded by mRNA, which is complementary to DNA.

Protein folding and modification occur post-translation, affecting the protein's function and transport.

Transcripts

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After learning about DNA, have you ever wondered, how can the DNA actually result in a trait?

Let's take an example - like eye color.

Yes, your DNA has the genetic information that codes for the color of your eyes.

Your eye color is based on a pigment that is inside the eyes.

But, in order to have that pigment, you have genes, which are portions of DNA, that can

code for proteins which help make that pigment.

So what we’re going to talk about is how your DNA can lead to the making of a protein.

This process is called protein synthesis.

Synthesis essentially means to “make something” so protein synthesis means to make protein.

And you may wonder, “What’s the big deal about proteins?”

Well you may not realize this but proteins are kind of a big deal.

They do all kinds of things.

Proteins are involved in transport, in structure, in acting as enzymes that make all kinds of

materials, in protecting the body…and so much more.

You've got to make proteins - it’s essential for you to live.

And what is so COOL is that you are making proteins right now as you sit and watch this

video.

It’s happening in your cells.

They’re making proteins.

So back to your DNA and its role in all of this.

All of your cells have DNA---well a few exceptions---and that DNA is in the nucleus.

Some DNA is noncoding DNA.

Some DNA makes up genes that are not activated.

More about that in our gene regulation video.

But we’re going to talk about genes that are coding for active proteins.

So how are we going to get the information from these genes out of the nucleus so that

the cell can start producing the proteins that it needs to make?

Well let us introduce you to the amazing work of RNA.

We have a video comparing and contrasting RNA---we’ll be brief here in saying that

RNA is a nucleic acid like DNA.

But it has a few differences.

Its role in protein synthesis also is HUGE.

Before we get into the process, please note our typical disclaimer: we tend to simplify

topics while staying as accurate as we can---but as always, we hope you will have the desire

to explore this complex, amazing process later on to learn all about the extra information

that we don’t have the ability to include in this short video.

In protein synthesis, we can look at two major steps.

One is transcription and the other is translation.

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.

I like a lot of alphabet mnemonics.

Now, transcription is when we’re going to transcribe the DNA into a message.

In your cells, the DNA is in the nucleus, so therefore, we’re doing transcription

in the nucleus.

In the step of transcription, an enzyme called RNA polymerase will connect complementary

RNA bases to the DNA.

These RNA bases are bonded together to form a single stranded mRNA.

The m in mRNA stands for messenger. Messenger RNA consists of a message made of RNA that has been based

on the DNA.

We do want to mention that this mRNA is not usually ready to go right away.

There's usually a significant amount of mRNA editing that occurs--- we highly encourage you to

do some reading about that because it’s not only fascinating---it’s critical for

the process to work correctly.

So what's something great about being mRNA?

Well in eukaryotes, you get out of the nucleus.

The mRNA can go out of the nucleus into the cytoplasm where it’s going to attach to

a ribosome.

Ribosomes make protein.

The ribosome is made of rRNA, and that’s an easy one to remember because the “r”

stands for ribosomal RNA.

The ribosome is going to build our protein in the next step called translation!

You know, you can find a lot of great clips and animations on translation that are just

fantastic.

We’re just going to break down some basics of what's happening.

In the cytoplasm, if you look at this, you have all these tRNA molecules available.

tRNA stands for transfer RNA.

They carry an amino acid on them.

An amino acid is the monomer for a protein; it's a building block for protein.

Since we’re making proteins, we’re going to need those amino acids to build it.

If you have a bunch of amino acids together, you can build a protein.

So it’s the tRNA that is going to bring those amino acids together to make that.

But wait, how does the tRNA know which amino acids to bring?

That’s why the mRNA, the message, is so important because it’s going to direct which

tRNAs come in and therefore which amino acids are transferred.

All of these tRNAs are looking for complementary bases.

When they find the complementary bases on the mRNA, they transfer their amino acid

When tRNA is bringing in the amino acids, it reads the bases---represented by these

letters here on the mRNA--- in threes.

So it doesn’t read one letter at a time; it reads it in triplets.

That’s called a codon.

So, for example, in this mRNA, the tRNA would read the codon AUG.

One of these tRNAs contains a complementary anticodon---which in this case is UAC.

All tRNAs that have the anticodon UAC will be carrying an amino acid called methionine.

A tRNA with the UAC anticodon comes in to pair with the complementary AUG codon

on the mRNA.

It transfers the amino acid it carries, methionine.

The tRNA will eventually leave, but it will leave behind its amino acid.

That’s the first amino acid before looking at the next codon.

Before we do the next codon to carry this on--- if you’re wondering---how did you

know that the tRNA that went with the AUG codon would be carrying an amino acid called methionine?

Well, for that, you will find a codon chart helpful!

You can learn to use a codon chart to determine which amino acid each mRNA codon will code

for.

Isn’t is so fascinating that scientists have been able to determine which amino acid

corresponds with these codons?

I used to have a codon chart poster and just marvel at that.

You can see on a codon chart that the AUG codon on the mRNA codes for methionine.

AUG is also considered a start codon as methionine is typically going to be your first amino

acid in proteins.

There are many types of amino acids in the codon chart, but there are even more possible

codon combinations.

That means there can be more than one codon that code for the same amino acid.

For example, according to the mRNA codon chart, all of these mRNA codons here code for the same

amino acid: leucine.

That means their complementary tRNAs all carry the same amino acid: leucine.

Ok, so going back to the mRNA---let’s try the next codon on this mRNA.

CCA.

On the codon chart, you can see that codes for the amino acid proline.

The complementary tRNA has the anticodon GGU and look, there’s the proline that we knew

it would be carrying.

The tRNA will transfer that amino acid and eventually leave where it can go pick up another

amino acid.

These amino acids are held together by a peptide bond.

And it will keep on growing.

Typically at the very end of the mRNA, there is a stop codon.

Stop codons do not code for an amino acid, but when the ribosome reaches it, it indicates

that the protein building is finished.

So the result of translation is that you built a chain of amino acids that were brought in

certain sequences based on the coding of the mRNA.

But remember that mRNA was complementary to the DNA.

So the DNA ultimately was the director of the entire protein building, of course, it

couldn’t have done it without some serious help from mRNA, rRNA, and tRNA.

Protein folding and modification may occur and the protein may need to be transported---this

can all vary based on the protein's structure and function.

Another fascinating topic for another Amoeba Sisters video.

Well that’s it for the Amoeba Sisters and we remind you to stay curious!