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Struktura e ADN-s : Nukleotidet

Cod. A23012005

Acidi deoksiribonukleik(ADN) ashtu si dhe acidi ribonukleik(ARN)jane te formuar nga nukleotidet. Cdo nukleotid eshte i formuar nga nje sheqer pentoz(ribozi) nga nje baze e azotuar(Adenine,Guanine,Citozine,Timine ne ADN ndersa ne ARN kemi Uracil ne vend te Timines)qe lidhen tek karboni 1 ,dhe nga grupet fosfat qe jane ne numer nga 1-3 cope.3 cope jane nese nukleotidi eshte ne formen e lire ndersa 1 nese eshte i lidhur ne zinxhirin e ADN ose ARN. Grupet fosfat lidhen tek karboni 5 .Besoj te gjithe keni degjuar per ATP qe eshte quajtur edhe si monedha e trupit tone.

Ndryshimi ne strukturen e sheqerit (nga i cili vjen edhe emri i secilit material gjenetik)eshte grupi qe eshte i lidhur me karbonin 2. Nese karboni 2 ka grup -OH eshte ARN,nese ka vetem -H eshte deoksiribo dmth ADN. Kjo eshte nje nga ndryshimet ndermjet ADN dhe ARN.

Bazat e azotuara jane 2 llojesh ne saje te numrit te unazave qe kane: Adenina dhe Guanina jane purina (kane 2 unaza ne strukture) kurse Citozina,Timina dhe Uracili jane piramidina(nje unaze ne strukture). Besoj edhe nga foto duket qarte qe Citozina eshte me 1 unaze.

Po te shihni mire struturen e nje nukleotidi do te vereni karbonet 3 dhe 5 qe jane te nje rendesie thelbesore per sa i perket bashkimit te nukleotideve ne nje zinxhir se dhe per menyren se si lexohet ADN. Te njejten figure do ta perdor edhe me vone(figure klas kjo,e thjeshte dhe te ndihmon shume per te kuptuar gjerat kryesore.Ma te mire nuk gjeta ne internet)

Deoxyribonucleic acid(DNA) like the ribonucleic acid(RNA) is composed of nucleotides. Every nucleotide is composed of three parts: a sugar molecule(pentose sugar) called deoxyribose(in RNA it is ribose and i'll explain the reason of why), one of four different nitrogen-containing compounds called bases which are Adenine,Guanine,Cytosine and Thymine(in RNA there is Uracile instead of Thymine),that are bound in the carbon 1,and a a phosphate group which may vary in number from 1 to 3 according to the situation whether the nucleotide is bound in the DNA chain or not. So there are 3 phosphate groups in the "free"form and only 1 when bound in the chain.the phosphate groups are bound in the carbon 5.
Ur gonna see later one of the nucleotides called adenosine triphosphate and its functions in the human body.


The difference in the sugar strucutre gives the name to the genetic material:if the carbon 2 has an -OH group(alcoholic group) it is RNA.when this group is not and there is only -H then it is DNA.this is one of the differences between DNA and RNA(take a look at the picture to understand it better)

Nitrogen-containing bases are divided in 2 types according to their ring numbers: purine(adenine and guanine which have 2 rings) and pyramidine(cytosine,thymine and uracile which have 1 ring).In the image u can see that cytosine has 1 ring.

Now consider again the structure of a nucleotide and pay attention to the carbon 3 and 5 because they have a particular importance in the union between 2 nucleotides and in the way the DNA is read.I'm gonna use the same picture later to explain the some other particularities.