Full transcript of “Introduction to Nucleic Acid Biochemistry”. Click a timestamp to open the video at that moment. Need another video? Use the YouTube transcript generator.
0:04 good day students you are welcome to another lecture episode on introduction to nucleic acid biochemistry so when we talk about nucleic acids we are going to be discussing about the molecules that are genetic carriers or the carriers of genetic information and we have two types of uh genetic carrier molecules molecules that carries genetic information uh we are talking about DNA
0:51 and RNA so these are the two types of nucleic acid that we are going to be uh discussing so first and foremost we talk about DNA and DNA is a molecule that is found in almost every living cell it serves as aary material containing biological instructions it contains biological instructions that make each human and other organism unique so it DNA it helps the cell to
1:39 make proteins and it also helps in facilitating reproduction it has from the structure you can see it has a twisted helical structure and it is double stranded it means two strand uh are joined together and it has uh some nucleotides that pairs with each other it has adenine that appears With Thine and guanine that appears with uh cyto adenine andine bond it is connected
2:29 via two hydrogen bonds and guanine pairs with cyto via three hydrogen bonds so we are going to discuss that in detail so DNA stands for deoxy ribonucleic acid deoxy ribonucleic acidd and the it is a chemical substance that is present in the nucleus of all cells in living organisms and it controls chemical changes that take
3:14 place in the cell so cells in the body you know different cells specialize to form different tissues and for each of those cells we talk about myocytes these are cells that are found in the moosul so cells that form mosles and ocytes that are found in the blood we have blood has we have the white blood cells and the red blood cells and we have the the nerve cells also and all these
4:00 cells that are formed they are controlled by the DNA so when we look at the DNA molecule in its entirety it is a very large molecule that is made up of long chain of subunits so DNA molecule uh is very long uh long molecule that is uh made up of what 10 of sub units and this sub units are what we call the the nucleotide so the subunits are called
4:48 nucleotide and each nucleotide is made up of a sugar that is called the oyos it is a f carbon sugar that is called deoxy ribos so it means it does not contain o h at position two of sugar and it has also a phosphate group and an organic an organic base nitrogenous base so nuclear acids and nucleotides when we talk about nucleic acids we are generally referring
5:36 to the DNA and the RNA DNA de oxy ribonucleic acid and RNA it's ribonucleic acid they are the carriers of what genetic information and the nucleic acids they are biological polymers that are made up of nucleotides and and they also call they also have pentos sugars Al pentoses that are linked to the purine or pamine base and also a phosphate group
6:22 so when we say purine molecules we are talking about those nucleotides that made up the uh the that's made up the the cells that is the building block of the DNA and also we have the the the PID so for the purines the purines are examples of P purins are
7:09 adenine rather examples of purines include adenine and guanine so Adine and guanine are purines while Pines include the cyto thamin and uracil CT U okay CTU for pins and AG adenine and Guin serve as uh as purines so for adenine it is abbreviated as aan abated as G and cyto abated as C tun
7:54 uril U so that is why the genetic code you is represented as actg and so on and so forth so for DNA you have your actg ording in combination depending on a pi with t and GP with C while in RNA you have you don't have t in RNA rather you have what we call urasil okay so urasil replace timing in RNA so in RNA you are going to have
8:55 so the the sugars that are found can be either the ribos or the oxy ribos as in the case of DNA or as a case of RNA or DNA respectively so in DNA we have the oxos while in R we have the ribos so if we look at the structure we have sugar and nitrogenous base to form what we call a uh a nucleoside so a nucleoside is is having sugar and a nitrogenous base and when a phosphate group is attached to the sugar we have what we call a
9:44 nucleotide and many of these nucleotides come together this is the monomeric unit the nucleotide to form the polymeric nuclic acid so the heterocycles that are found in DNA and RNA we have the adenine Quine cytosin and thamin that are found in DNA and DNA while in RNA we have uril in place of timing and structurally and this is how they look like we have the adenine that is represented as a can be found in both DNA and RNA and we have the
10:30 Quan that is can be found in both DNA and RNA and we have the cyto that is found in DNA and RNA then thine that is only found in DNA and urasil only found in RNA remember in terms of whether it is purine or purine uh nitrogenous base uh we we said that uh adenine and guanine are purines while cyto thine and uracil are
11:20 pins so the O ribonucleotides that are found in DNA uh for the nucleotid and there are symbols and also the nucleotides so nucleotides are the combination of the nitrogenous base the sugar and the phosphate group while the nucleoside is the nitrogenous base the sugar without the phosphate group and they have their own representation So structurally when you say de oxy adalite it is De oxy adinos five Prime monophosphate and it can be represented as as a o a or the M
12:09 okay so um for the nucleoside form it is called deoxy adenosine and it is represented as da for the next one it can be represented as g d g or D GM P that is the oxy guate or the oxy guanosine 5 Prime on phosphate and the nuc side is the oxy guanosine and represented as as the G so also for the thine you have DT for the de oxyamine as the nucleo side so also DC for the oedin for
12:59 cyto nucleosides and you have the different nucleotides here represented so for the de oxy ribonucleotide that is those that are found within the an we have the two prime deoxyadenosine five Prime monop phosphate and we have the two prime oxy onein five Prime Prime monophosphate as in the case of either iDine that is here or guanine and if cyto we have 2 Prime de oxin five Prime phosphate and we have the foramin is 2 Prime
13:45 oxyamine 5 Prime phosphate so this they are found in the DNA okay they are the oxyon nucleotid they are found in DNA when while here the the the the oxy ribonucleotides that are found in the DNA also so it's still uh the same uh representation here so the hydrogen bonding interaction so two bases can form hydrogen bond between them for monom large number of base pairs is uh is
14:32 possible for in in while in Pol nucleotide only few possibilities exist so if you look at whatson Creek based PA pred dominate in double stranded DNA where adenine pairs with thine two hydrogen bonds cytosine pairs with Quine with two hydrogen bonds so these are purine pairs that pairs with the uh p okay so the building block molecule of nucleic acids are the nucleotides in RNA we have the CMP GMP and TMP while in D in DNA we have the D the
15:22 the CMP uh the the GMP and the U so functions of nucleotid and nucleic acids so um nucleotid functions they function in uh for energy metabolism where ATP is the uh energy currency that's the universal energy currency and all living organisms utilizes energy in form of ATP
16:11 and they also they are found in in enzyme co-actors such as adenine nicotinamide adenine D nucleotide serve as a co-actor for some enzymes and also in Signal trans transaction such as cyclic so for nucleic acid uh function the functions in form of storage of genetic information in DNA transmission of genetic information in Binger RNA in processing of genetic information ribosomes and protein synthesis where you have drna Transfer RNA and ribosomal
16:59 AR so the linkage between the molecules is in form of phosphor di linkage or phosphor di Bri you have the three Prime Terminal and also five Prime teral in the nucleotide residual so nucleotide composition is of three parts we have the de oyibos sugar without the oxygen in the to carbon and we have phosphate group we have one of the four types of bases that are all nitrogen containing we have the adamine adenine thine that is only found in DNA and cytosine that is uh found in uh both DNA and RN and
17:45 Guan also so best paing in is based on the Wason Creek model in 1953 if you remember from our previous uh lecture video on the history of science that made scientist that made contribution scientist that made contribution breakthrough in Biochemistry you remember in 1853 Wason and Creek they noted that DNA consists of two Pol nucleotide strand running in opposite direction and they coil around each other in a double helix and the strands are held together by hydrogen bonds between specific base pairs and adenine and thamin form strong hydrogen
18:31 bonds with each other okay in two hydrogen bonds with each other but not they don't form hydrogen means a do not pair with G or C and T do not pair with t with C or G rather C pairs with G so G and cyto and guanine form strong hydrogen bonds between each other but they do not form uh hydrogen bonds between uh G and a or G T or C and A O C and T so the GC hydrogen bond is three while the aogen bond is two and the difference in the Strand are that the strand of DNA are complementary because
19:16 of hydrogen bond and wherever G occurs in one strand is C occurs in the opposite in the other opposite strand okay because you remember remember the double helical nature of the DNA okay so in the double stranded one strand of the DNA if a is there in one strand opposite to it that they form the hydrogen bond you must see a t that is going towards the opposite direction so when an a occurs in one Str a t occurs in the other Str as simple as that so if you look at the base pairing and the arrangement the phosphor diester
20:03 linkage is in three frame five Prime Direction so we look at the phosphate Bridge here phos forer Bridge here okay that link one nucleotide one nucleotide to another to form a continuous uh polymeric unit DNA so the primary structure of nucleic acid it uh is that you have a nucleotide phosphate group sugar and nitrogenous base that forms a with that reacts with another link with another nucleotide with the formation of an ester bond to form phospho diester Bond
20:50 so you have it the five Prime oh sorry the three prime o of one nucleotide form uh a a bond with the oxygen or the phosphate group of another molecule of the nucleotide in the five Prime uh uh position so you have what the five Prime free five Prime phosphate that is ready to be attached to another nucleotide that is having the O3 Prime and you have what threee o here fre Hydrox group that is ready to attach to another five Prime
21:37 three five Prime phosphate of another nucleotide so that is how the molecule build up the polymer Builds on so the primary structure of nucleic acid is the what nucleotide sequence and the nucleotid in nucleic acid are join by phospho diester Bond and O 3 Prime o of the sugar in one nucleotide forms an esta bond to the phosphate group on the F Prime carbon of the other sugar that is next in the
22:22 nucleotide so generalized structure of DNA looks like you have five Prime three five Prime phosphate group the end and you have phosphate group the sugar attached to the base the phate group attached in the next nucleotide and you have the phosphate group sugar base and the three prime and fre okay this is how it looks like uh similar to what we uh demonstrated so the rum primary structure looks like like this where you have a and you have C here you have G have t in what you have the in five
23:10 Prime three prime direction or three prime five Prime Direction and for the next strand it will be the three prime five Prime Direction so a nucleus a nuclic acid polymer has a free P Prime phosphate group at one end and a free three Prime oh group at the other end the sequence is read from the three five prime using the letters of the bases from the three five Prime you have a c d t that's how you read it from five Prime to three prime and this example read as what P prime a c g T3 Prime that is how the sequence
23:56 read example of DNA Prime structure the the ox nucle acid here 3 Prime okay and you have the the adenine here adenine is here while here is cyto you have your three prime phosphor diester Bond and you have another three prime prime phosphor diester Bond so this is how it's uh looks like five prime a c d c three frame so in the DNA we have AC GT are links by three prime five Prime
24:42 phosphor diester bonds between the the oxos and the phosphate group so nuclic acid structure the polymerization looks like this okay you have your a g a and guine here adenine here thine and cyto here and you have three prime three five Prime phosphate end here and the three prime or hydroxy group three here so you have a sugar phosphate backbone and you have the nucleotides and it looks like this in DNA and and also in the RNA so you remember in DNA you have what
25:29 the the oxos and while in R you have the the Ros so the sequences can be described as to be said is a chain that is from five Prime and identifying the bases in order of their occurrence using the abbreviations a for adenosine G for guanosine c for citadine and T for iDine or U for uril in R and typical sequence is written as t a g d c so properties of DNA is a double helic it's a double hel double helical nature
26:15 and the strand of the DNA is anti parallel it means one strand is is opposite to the other strand if one strand is going from P Prime to 30 prime the other strand will go uh in three prime P Prime Direction with G pairs with C can see G pair with C with three hydrogen bonds and a pairs with t with two hydrogen bonds and the Strand are complementary there are hydrogen bond forces okay so the Str are complementary in that the number of G are equals to the number of c and number of a are equals to the number of T there are base stacking interactions and there are 10
27:03 base pairs per per ton before each tone because it's it's twisted helical before each tone there are 10 B so this is another representation of how the structure look likees okay so for the five Prime three prime Direction looks like this while the three prime uh the five Prime three Prime in the opposite direction it looks inverted so um thank you we are going to stop here uh when we come next we will discuss uh uh more on the uh
27:48 possible combination uh and also the uh more explanation so if you have any question you can drop it at the comment section and you are uh going to be covered and it's going to be addressed thank you see you in the next video
