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NEUCLOTIDES METABOLISIM
Purine and pyrimidine structures and
functions:
❖ Pyrimidines (thymine, cytosine, and uracil)
composed from one ring made from 6 carbons
while purines (adenine and guanine) composed
from 2 rings → five membered ring and six
membered ring fused to each other.
❖ Since nucleotides contain purines or pyrimidines
(nitrogenous bases) therefore nucleotides
considered as a one of the nitrogen containing
compounds.
❖ Purines and pyrimidines are very important
molecules that are found in nucleotides and serve different functions:
1) Essential for RNA and DNA synthesis (deoxyribonucleic acid and ribonucleic acid).
2) They serve as carriers of activated intermediates in the synthesis of some
carbohydrates, lipids, and conjugated proteins, such as, UDP-glucose (glycogen
synthesis) and CDP-choline (membrane lipid synthesis).
3) They are structural components of several essential coenzymes, such as coenzyme A,
FAD, NAD+, and NADP+.
4) They serve as second messengers in signal transduction pathways, such as cAMP and
cGMP.
5) They are “energy currency” in the cell (ATP).
6) They act as allosteric regulatory compounds for many metabolic pathways by
inhibiting or activating key enzymes (eg: ADP, AMP ….).
Nucleosides:
❖ This method is used to name compounds that contain only sugar and a nitrogenous base,
to indicate the number of phosphates that the compound contains.
The main rule → (Nucleoside= Pentose sugar + Base).
Eg: ATP can be named as adenosine Triphosphate, “sine” suffix is used to indicate the
presence of nucleoside (sugar + nitrogenous base) as well as the number of phosphate
groups attached to the nucleoside. However, ATP can be named as a “Nucleotide” with
no indication for the number of phosphate groups.
, ❖ (Ribose + base = Ribonucleoside).
Eg: The ribonucleosides of A, G, C, and U are named
adenosine, guanosine, cytidine, and uridine, respectively.
❖ (2-deoxyribose + base = deoxyribonucleoside.)
Eg: The deoxyribonucleosides of A, G, C, and T are named
deoxyadenosine, deoxyguanosine, deoxycytidine, and
deoxythymidine, respectively. (Deoxy sugars are sugars that have
had a hydroxyl group replaced with a hydrogen atom).
Recall: the carbons in the sugar molecule are numbered with a prime 1’, 2’
while the carbons of the nitrogenous bases are named without prime (Observe the picture).
Nucleotides:
❖ This method is used to name compounds that contain sugar,
nitrogenous base and phosphate without any indication for the
number of phosphates that the compound contain.
(Nucleoside + one or more phosphate groups= Nucleotide).
❖ The first P group is added by an ester linkage to the 5'-OH of
the pentose forming a nucleoside 5'-phosphate or a 5'-
nucleotide. The second and third phosphates are each
connected to the nucleotide by a “high-energy” bond.
(Nitrogenous base is added to the pentose on the 1’ carbon and the phosphate group is added on the 5’
carbon).
Recall: The phosphate groups are negatively charged causing DNA and RNA to be nucleic acids.
Base modification:
❖ Nitrogenous bases specifically in the DNA or RNA structures are more
susceptible for further covalent epigenetic modifications. Therefore,
Acetylation
nucleotide sequences are more able to be recognized by specific enzyme or
to be protectable from degradation from certain nucleases.
❖ *Methylation for nitrogenous bases is important in gene silencing →
preventing transcription factors from binding accordingly no gene Reduction
expression occur.
*Acetylation for nitrogenous bases is usually associated with gene
activation → allowing for transcription factors to bind accordingly more
Methylation
activation for gene expression. `
*Reduction is important in URICIL.
*Glycosylation by adding sugars.
NEUCLOTIDES METABOLISIM
Purine and pyrimidine structures and
functions:
❖ Pyrimidines (thymine, cytosine, and uracil)
composed from one ring made from 6 carbons
while purines (adenine and guanine) composed
from 2 rings → five membered ring and six
membered ring fused to each other.
❖ Since nucleotides contain purines or pyrimidines
(nitrogenous bases) therefore nucleotides
considered as a one of the nitrogen containing
compounds.
❖ Purines and pyrimidines are very important
molecules that are found in nucleotides and serve different functions:
1) Essential for RNA and DNA synthesis (deoxyribonucleic acid and ribonucleic acid).
2) They serve as carriers of activated intermediates in the synthesis of some
carbohydrates, lipids, and conjugated proteins, such as, UDP-glucose (glycogen
synthesis) and CDP-choline (membrane lipid synthesis).
3) They are structural components of several essential coenzymes, such as coenzyme A,
FAD, NAD+, and NADP+.
4) They serve as second messengers in signal transduction pathways, such as cAMP and
cGMP.
5) They are “energy currency” in the cell (ATP).
6) They act as allosteric regulatory compounds for many metabolic pathways by
inhibiting or activating key enzymes (eg: ADP, AMP ….).
Nucleosides:
❖ This method is used to name compounds that contain only sugar and a nitrogenous base,
to indicate the number of phosphates that the compound contains.
The main rule → (Nucleoside= Pentose sugar + Base).
Eg: ATP can be named as adenosine Triphosphate, “sine” suffix is used to indicate the
presence of nucleoside (sugar + nitrogenous base) as well as the number of phosphate
groups attached to the nucleoside. However, ATP can be named as a “Nucleotide” with
no indication for the number of phosphate groups.
, ❖ (Ribose + base = Ribonucleoside).
Eg: The ribonucleosides of A, G, C, and U are named
adenosine, guanosine, cytidine, and uridine, respectively.
❖ (2-deoxyribose + base = deoxyribonucleoside.)
Eg: The deoxyribonucleosides of A, G, C, and T are named
deoxyadenosine, deoxyguanosine, deoxycytidine, and
deoxythymidine, respectively. (Deoxy sugars are sugars that have
had a hydroxyl group replaced with a hydrogen atom).
Recall: the carbons in the sugar molecule are numbered with a prime 1’, 2’
while the carbons of the nitrogenous bases are named without prime (Observe the picture).
Nucleotides:
❖ This method is used to name compounds that contain sugar,
nitrogenous base and phosphate without any indication for the
number of phosphates that the compound contain.
(Nucleoside + one or more phosphate groups= Nucleotide).
❖ The first P group is added by an ester linkage to the 5'-OH of
the pentose forming a nucleoside 5'-phosphate or a 5'-
nucleotide. The second and third phosphates are each
connected to the nucleotide by a “high-energy” bond.
(Nitrogenous base is added to the pentose on the 1’ carbon and the phosphate group is added on the 5’
carbon).
Recall: The phosphate groups are negatively charged causing DNA and RNA to be nucleic acids.
Base modification:
❖ Nitrogenous bases specifically in the DNA or RNA structures are more
susceptible for further covalent epigenetic modifications. Therefore,
Acetylation
nucleotide sequences are more able to be recognized by specific enzyme or
to be protectable from degradation from certain nucleases.
❖ *Methylation for nitrogenous bases is important in gene silencing →
preventing transcription factors from binding accordingly no gene Reduction
expression occur.
*Acetylation for nitrogenous bases is usually associated with gene
activation → allowing for transcription factors to bind accordingly more
Methylation
activation for gene expression. `
*Reduction is important in URICIL.
*Glycosylation by adding sugars.
