now the second part of this chapter that we're going to be looking at is something known as protein synthesis in the previous videos we have introduced DNA we have also talked about RNA the three types of RNA mRNA trnes and also rrnas now what do these nucleic acids have to do uh what are their functions how are they important for our lives the answer is all the nucleic acids DNA and RNA are important for one process inside the cell known as protein synthesis and what exactly is protein synthesis well to put it bluntly it is just the production of proteins within the cells now cells synthesize different types of proteins to carry out specific functions for example B lymphocytes will produce certain proteins known as antibodies to protect our bodies from infections goblet cells in our intestinal lining and also our tracheal lining will produce mucus which is a particular protein that is needed to trap dust and pathogens in our Airway or also our intestines erythroblasts I don't have to memorize this one though erythroblasts which are the cells before they become red blood cells a little blast will have to produce proteins known as hemoglobins needed to carry oxygens when they become mature with blood cells and last but not least beta cells in your pancreas they have to synthesize proteins known as insulin which helps to control our blood glucose concentration so these are specific cells in our body and they produce specific types of proteins that carry out specific functions so the antibodies mucus hemoglobin and Insulin are all proteins but they all have different structures and they all have different functions as we've discussed this a little bit in chapter two when we talked about amino acids and proteins so long story short there are so many different types of proteins right so how does the cell know which protein it has to produce because a cell can have the capability of producing any types of pollutants that I've just listed up and then some but how does the cell know that oh I need to produce this protein and not that protein so before we talk about that in detail we kind of want to cover a little bit about just an overview on the relationship between DNA rnas and amino acids if you want to study a little bit more amino acids you can go back to my playlist and check back uh chapter 2 where I talk about amino acids and proteins now so for example in eukaryotic cells or in eukaryotes where they have a nucleus inside the nucleus the DNA or the chromatin is found and the DNA as we've discussed is just basically a type of nucleic acid that has a double helix shape now parts of the DNA where I'm highlighting over there will be referred to as something called genes so what exactly is a gene a gene is basically a base sequence of the DNA that codes for polypeptides or that codes for a specific polypeptide so a lot of times when I ask my students what's the meaning of a gene students will say oh Gene is a part of the DNA and it produces polypeptides no that is raw that definition is wrong it's technically wrong because the gene itself does not produce the protein the Gene tells the cells how to build a polypeptide that is a very important thing to know it is more like a manual okay like if you've ever assembled furniture or even built Legos okay when you're building Legos like when you're putting the blocks together the when you look at the manual on which piece to put which piece to put second and which piece to put but the manual is acting as the gene the manual itself does not build the Lego blocks for you it just acts as a guide that is what the gene is doing okay it provides the information for the cell so that the cell can produce or synthesized the specific polypeptide or protein now if the gene is the manual then which part of the cell is supposed to produce the polypeptide then the gene will have to provide its information to be ribosome because the function of the ribosome is to synthesize polypeptides so for example if the gene says Hey make the polypeptide but the right the gene is inside the nucleus and the ribosome is in the cytoplasm they are so far away from each other the ribosome cannot hear that the ribosome cannot hear the order so because they are separated by the nuclear membrane right so how does the gene provide the information to the ribosome it provides the information to the ribosome by first copying itself or transcribing itself to produce something called the MRNA how this happens we will look at it in the next video but long story short you can just basically say the gene is transcribed or copied to produce something known as an mRNA now what does the MRNA do the MRNA will then move towards the ribosome so remember earlier where the Gene and ribosome were far away and they cannot meet each other the MRNA acts as the middle person so the MRNA takes the information from the Gene and gives it to the ribosome and once the ribosome receives the MRNA the ribosome is like oh I now know how to make the polypeptide but then comes the second problem the second problem is well I know how to make the polypeptide but I don't have the ingredients to make the polypeptide so what are the ingredients needed to build the polypeptides the ingredients it needs to build the polypeptides are amino acids so because poly peptides are basically made by joining one amino acid to another so where do the amino acids come from well very simple the amino acids will then come from trnas and as you can see I'm blowing up the TRNA over there and the TRN is I'm just blowing out 60 rnas okay and each of the TRNA are attached to different types of amino acids as I have represented by different colors all right so what the trnas will then do is the trnas will then bring the amino acids to the ribosome and as they bring the amino acids to the ribosome the ribosome will then join those amino acids together to synthesize the polypeptides so long story short the gene is transcribed to produce the MRNA the MRNA will move towards the ribosome in the cytoplasm the trns will bring the amino acids to the ribosome and the ribosome will then synthesize the polypeptides that is needed by the cell that's how it works so that kind of answers the question on the relationship between D and A mRNA TRNA and rrna which make up the ribosomes so they all work together so that the cell is able to synthesize a specific polypeptide now I've answered the question as an overview of how the cell produces a polypeptide but how does the cell produce different types of polypeptides the answer is quite simple as you can see in this nucleus here I'm drawing out two chromatins okay as you can see in the nucleus and each of the chromatin has a different Gene the chromatin on the top has Gene a which I've labeled which I've highlighted in yellow and the chromatin at the bottom has Gene B which I've highlighted in pink I think that's pink yeah that's pink it looks like pink purple pink yeah I sometimes I have difficulty with colors but you get my point now the difference between Gene a and Gene B is their base sequences are slightly different okay the B sequences of Gene a and the base sequences of Gene B slightly different let's not get into let's not go into the details yet so let's say as you can see I have tRNA molecules over here now my tierneys look a little bit different I've just simplified the tRNA molecules I like drawing them I know they're supposed to have a clover shape I get it okay but I just like drawing them in that square okay the the circles of different colors at the top represent the amino acids and the three bases at the bottom represent the anticodons do not worry if you don't understand my diagram just understand that I I like to represent a symbolize trnas in this way all right uh if you still don't understand don't worry we will be looking at the process in detail in future videos all right but now just imagine them to be tRNA molecules so what happens is there's a ribosome there the ribosome is made up of rrnas and some proteins so first let's say the cell wants to produce a particular type of protein in gene a undergoes transcription or Gene a is copied to produce the MRNA the MRNA will then move towards the ribosome giving the information to the ribosome once the ribosome has the information specific tRNA molecules will then move towards the ribosome bringing its amino acids together and when the ribosome receives the amino acids the ribosome will synthesize the polypeptide in this example I'm going to call it polypeptide a so Gene a provides information for the cell to produce polypeptide a let's look at Gene B Gene B undergoes the same process it will produce the MRNA by ah being copied or transcription the MRNA will then move towards the ribosomes and in this case the TRNA brings the information to the ribosomes and the ribosome synthesizes the polypeptide but as you can see over here when it produces polypeptide B compare it to polypeptide a are they exactly the same no they are not polypeptide a is longer made up of six amino acids and polypeptide B is a shorter made up of four amino acids and the amino acid sequences are different as I've represented in the colors as well so I'm sorry if you're colorblind and if you can't notice the difference between the color but notice that the difference between the uh what I'm just trying to say is the amino acid sequence in polypeptide a and the amino acid sequence in polypeptide B are different because the information came from two different genes so Gene a will tell the cell to produce polypeptide a which is a type of protein and Gene B will tell the cell to produce a different type of polypeptide which is poly peptide B that's how the cell is able to produce different types of proteins because the cell has different types of genes that's basically it