Biofelsefe — Nükleotid
NFA 2020 / Aziz Yardımlı



Biofelsefe — Nükleotid




Nucleotide (W)

This nucleotide contains the five-carbon sugar deoxyribose (at center), a nitrogenous base called adenine (upper right), and one phosphate group (left). The deoxyribose sugar joined only to the nitrogenous base forms a Deoxyribonucleoside called deoxyadenosine, whereas the whole structure along with the phosphate group is a nucleotide, a constituent of DNA with the name deoxyadenosine monophosphate.

Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monomeric units of the nucleic acid polymers deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecules within all life-forms on Earth.

Nucleotides are composed of three subunit molecules: a nitrogenous base (also known as nucleobase), a five-carbon sugar (ribose or deoxyribose), and a phosphate group consisting of one to three phosphates. The four nitrogenous bases in DNA are guanine, adenine, cytosine and thymine; in RNA, uracil is used in place of thymine.

Nucleotides also play a central role in metabolism at a fundamental, cellular level. They provide chemical energy — in the form of the nucleoside triphosphates, adenosine triphosphate (ATP), guanosine triphosphate (GTP), cytidine triphosphate (CTP) and uridine triphosphate (UTP) — throughout the cell for the many cellular functions that demand energy, including: amino acid, protein and cell membrane synthesis, moving the cell and cell parts (both internally and intercellularly), cell division, etc. In addition, nucleotides participate in cell signaling (cyclic guanosine monophosphate or cGMP and cyclic adenosine monophosphate or cAMP), and are incorporated into important cofactors of enzymatic reactions (e.g. coenzyme A, FAD, FMN, NAD, and NADP+).

In experimental biochemistry, nucleotides can be radiolabeled using radionuclides to yield radionucleotides.



Structure (W)

Showing the arrangement of nucleotides within the structure of nucleic acids: At lower left, a monophosphate nucleotide; its nitrogenous base represents one side of a base-pair. At upper right, four nucleotides form two base-pairs: thymine and adenine (connected by double hydrogen bonds) and guanine and cytosine (connected by triple hydrogen bonds). The individual nucleotide monomers are chain-joined at their sugar and phosphate molecules, forming two 'backbones' (a double helix) of a nucleic acid, shown at upper left.

A nucleotide is composed of three distinctive chemical sub-units: a five-carbon sugar molecule, a nitrogenous base — which two together are called a nucleoside — and one phosphate group. With all three joined, a nucleotide is also termed a "nucleoside monophosphate", "nucleoside diphosphate" or "nucleoside triphosphate", depending on how many phosphates make up the phosphate group.


Nucleic acids then are polymeric macromolecules assembled from nucleotides, the monomer-units of nucleic acids. The purine bases adenine and guanine and pyrimidine base cytosine occur in both DNA and RNA, while the pyrimidine bases thymine (in DNA) and uracil (in RNA) occur in just one. Adenine forms a base pair with thymine with two hydrogen bonds, while guanine pairs with cytosine with three hydrogen bonds.

In addition to being building blocks for construction of nucleic acid polymers, singular nucleotides play roles in cellular energy storage and provision, cellular signaling, as a source of phosphate groups used to modulate the activity of proteins and other signaling molecules, and as enzymatic cofactors, often carrying out redox reactions. Signaling cyclic nucleotides are formed by binding the phosphate group twice to the same sugar molecule, bridging the 5'- and 3'- hydroxyl groups of the sugar. Some signaling nucleotides differ from the standard single-phosphate group configuration, in having multiple phosphate groups attached to different positions on the sugar. Nucleotide cofactors include a wider range of chemical groups attached to the sugar via the glycosidic bond, including nicotinamide and flavin, and in the latter case, the ribose sugar is linear rather than forming the ring seen in other nucleotides.


Structural elements of three nucleotides—where one-, two- or three-phosphates are attached to the nucleoside (in yellow, blue, green) at center: 1st, the nucleotide termed as a nucleoside monophosphate is formed by adding a phosphate (in red); 2nd, adding a second phosphate forms a nucleoside diphosphate; 3rd, adding a third phosphate results in a nucleoside triphosphate. + The nitrogenous base (nucleobase) is indicated by "Base" and "glycosidic bond" (sugar bond). All five primary, or canonical, bases—the purines and pyrimidines—are sketched at right (in blue).
Examples of non-nucleic acid nucleotides

, a cyclic nucleotide signaling molecule with a single phosphate linked to both 5- and 3-positions.

, a nucleotide signaling molecule with both 5'- and 3'-phosphates.

a dinucleotide enzymatic cofactor.

, a dinucleotide enzymatic cofactor in which one of the ribose sugars adopts a linear configuration rather than a ring.



Synthesis (W)





Pyrimidine ribonucleotide synthesis

Pyrimidine ribonucleotide synthesis (W)

The synthesis of UMP.
The color scheme is as follows: enzymes, coenzymes, substrate names, inorganic molecules.

Main article: Pyrimidine metabolism


(S)-Dihydroorotate + O2 → Orotate + H2O2



Orotidine 5'-monophosphate






Purine ribonucleotide synthesis

Purine ribonucleotide synthesis (W)

Main article: Purine metabolism

The atoms that are used to build the purine nucleotides come from a variety of sources:

The synthesis of IMP. The color scheme is as follows:
enzymes, coenzymes, substrate names, metal ions, inorganic molecules

The biosynthetic origins of purine ring atoms

N1 arises from the amine group of Asp
C2 and C8 originate from formate
N3 and N9 are contributed by the amide group of Gln
C4, C5 and N7 are derived from Gly
C6 comes from HCO3 (CO2)



  • GART (reactions 2, 3, and 5)
  • PAICS (reactions 6, and 7)
  • ATIC (reactions 9, and 10)







Pyrimidine and purine degradation

Pyrimidine and purine degradation (W)



Unnatural base pair (UBP)

Unnatural base pair (UBP)

Unnatural base pair (UBP) (W)




Length unit

Length unit

Length unit (W)



Nucleotide supplements

Nucleotide supplements

Nucleotide supplements (W)


Another study conducted in 2013 looked at the impact nucleotide supplementation had on the immune system in athletes. In the study, all athletes were male and were highly skilled in taekwondo. Out of the twenty athletes tested, half received a placebo and half received 480 mg per day of nucleotide supplement. After thirty days, the study concluded that nucleotide supplementation may counteract the impairment of the body's immune function after heavy exercise.


Abbreviation codes for degenerate bases

Abbreviation codes for degenerate bases

Abbreviation codes for degenerate bases (W)

Main article: Nucleic acid notation


Symbol Description Bases represented
A adenine A 1
C cytosine C
G guanine G
T thymine T
U uracil U
W weak A T 2
S strong C G
M amino A C
K keto G T
R purine A G
Y pyrimidine C T
D not C (D comes after C) A G T
H not G (H comes after G) A C T
N any base (not a gap) A C G T 4






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