Okay, this is chapter 3, objective 5. This is discussing how proteins get created. So we're first going to start with DNA, which has the instructions on how to make a protein, and then that DNA is going to write down the directions for that specific protein in the form of a messenger RNA strand, which is then going to go out to a ribosome, and the ribosome is going to put together the amino acids in the right sequence. to create the protein.
So protein synthesis consists of two phases, transcription and translation. So let's talk about transcription first. Transcription is going to happen in the nucleus.
This is where the double-stranded DNA is going, and again, that double-stranded DNA has got the instructions on how to make a bazillion proteins, okay? But we just need the information on how to make one specific protein. So maybe just this little piece of the DNA right here might get written down into a messenger RNA strand.
Now, because DNA is in the nucleus all the time, it can never leave the nucleus, it will write the instructions on a messenger RNA strand, which, as you can see, will leave the nucleus. Okay, so the process of going from DNA to messenger RNA, that's transcription. Now, once the messenger RNA goes out and finds a ribosome, which is made up of a large and a small subunit, the messenger RNA strand and the ribosome undergo what's called translation.
So that's the second part. So the ribosome translates the information on the messenger RNA strand and puts together the protein, also known as a polypeptide. So transcription, just to show you just by itself what's going on here, and again, this takes place in the nucleus.
This is where you have the DNA nucleotides being written onto a strand of RNA or in the form of RNA nucleotides. So that's why it's transcription. It's literally writing it from nucleotide to nucleotide.
So you've got your DNA, double-stranded DNA here, which is represented in the blue, and then you have the RNA, which is represented by pink. You should be able to tell a DNA strand versus an RNA strand without me telling you, just simply because DNA is going to have that thymine present, where RNA is going to have uracil present. So just looking at the nucleotides in the strand, you should be able to tell me whether it's DNA or RNA.
And again, the DNA is only copied from here to here for this particular protein. Beyond... That's a different protein that it's being coded for, right? So you don't code that far up. So again, just reminding you all that the DNA has got the instructions on many, many, many, many proteins.
So it's only going to transcribe the protein that's required. Translation occurs in the cytoplasm at a ribosome. So again, you've got your large and your small subunit here.
You have your messenger RNA strand, which is being read by the ribosome. And then you have, so you've got your messenger RNA strand, which provides the information on how to make the protein. You have the ribosome, which is going to put the amino acids in the right sequence, but you have to get the amino acids from somewhere.
So the tRNA molecule, also known as transfer RNA, transfers the... amino acid from one location in the cell and brings it to the ribosome. So the ribosome has the materials it needs to put the protein together in the right order. So all of these little blue circles right here, these are all amino acids.
And when you get them all joined together by peptide bonds, since the word polypeptide, all joined together by peptide bonds, you have your protein. This again, there's a hyperlink here to a three minute video on it. transcription and translation.
Not bad, probably a little more than you need, but it's a pretty good video. So you have here the transcription which is occurring in the nucleus, and that is the process of DNA transcribing the section on how to build a protein into a messenger RNA strand. That messenger RNA strand is going to leave the nucleus by way of a nuclear pore. It is then going to go out and meet up with the large and small subunits of a ribosome. The ribosome is going to put the amino acids together in the right order when the tRNA molecule brings in the amino acids so that the ribosome can put them together in the right order.
And here's a video here over transcription and translation. Again, if you just wanted to see another visual on how that works. And that is objective five.