Nucleotides are organic molecules that contain pentose, a nitrogenous base, and a phosphate group.
They are the monomers of the nucleic acids DNA and RNA, but they are also important as free molecules such as ATP and GTP.
What are nucleotides?
They are organic molecules formed by the covalent union of a five-carbon monosaccharide or pentose, a phosphate group, and a nitrogenous base. The part of the nucleotide that is formed only by the nitrogenous base and the pentose is known as a nucleoside.
Structure:
Each nucleotide is an assembly of several components:
Phosphoric acid: Its formula is H3PO4. Each nucleotide can contain from one to three.
Isoaloxacinic nitrogenous bases: It is flavin (F). It is not found in DNA or RNA, but in compounds such as FAD.
Pyrimidine nitrogenous bases: They are known as thymine (T), cytosine (C) and uracil (U). Thymine and cytosine are part of DNA and in RNA we find cytosine and uracil.
Purine nitrogenous bases: Known as adenine (A) and guanine (G). Both are found in DNA and RNA.
Nitrogenous bases: These are those derived from the heterocyclic aromatic compounds purine and pyrimidine.
Pentose: It is a sugar with five carbon atoms. It can be ribose, which is part of RNA, or deoxyribose, which is part of DNA.
Characteristics OF Nucleotides:
Among the characteristics of nucleotides we have:
- They constitute nucleic acids such as DNA and RNA.
- They form chemical bonds in cellular systems in response to hormones and other extracellular stimuli.
- They are structural components of enzymatic cofactors and metabolic intermediates.
- They are constituents of nucleic acids, deoxyribonucleic acid (DNA) and the structure of proteins, biomolecules and cellular components comes from the information programmed in a sequence of nucleotides.
- They are important for cellular metabolism.
Different Types of Nucleotides:
Among the different types of nucleotides we have:
AMP
It is an adenine nucleotide with a phosphoric acid esterified with the 5′ and 3′ carbons of ribose, this gives it a cyclic structure.
Its function is to act as a second messenger, activating enzymes that regulate certain chemical reactions in the cell when hormones arrive.
ADP
Known as adenosine diphosphate, it is a nucleotide diphosphate stored in the granules of platelets and is mobilized through platelet activation.
It is a molecule with high energy power, important for various reactions. In addition, it is recycled and another phosphate is added to convert it into ATP.
ATP
Adenosine triphosphate is a molecule used by all living organisms to provide energy for chemical reactions. In addition, it is a precursor of certain essential coenzymes such as NAD+ or coenzyme A. Its molecular formula is C10H16N5O13P3.
It is one of the four monomers used in the synthesis of cellular AR. It is also a phosphate group transfer coenzyme that binds to kinase enzymes.
It is the main source of energy for the vast majority of cellular functions such as the synthesis of macromolecules such as DNA, RNA and proteins.
GTP
Guanosine triphosphate, also known as guanosine-5-triphosphate, is one of the nucleotide triphosphates used in cellular metabolism . Its structure is C10H16N5O14P3.
Its main function is to carry energy in the form of phosphates. It is also essential in some signaling pathways and acts as an activator of substrates in metabolic reactions.
cGTP
It is known as cyclic guanosine triphosphate and helps cyclic adenosine monophosphate in the function of activating ion channels regulated by cyclic nucleotides in the olfactory system.
NAD and NADP
They are substances formed by the union of two nucleotides through a phosphodiester bond. One contains adenine and the other nicotinamide (niacin or vitamin B3) is a nitrogenous base derived from pyrimidine.
NAD+ is an oxidized form and is an acceptor that intervenes in the exchange of electrons and protons for the production of energy in the cell . When reduced to NADH it carries two electrons and one proton. This nucleotide is necessary in glycolysis and the Krebs cycle.
NADP has the same functions and structure , with the difference that it includes a phosphate group on the 2′ carbon of the ribose attached to adenine. This nucleotide is involved in photosynthesis.
FLAVIN nucleotides
They are made up of a flavin nitrogenous base linked to ribitol, a type of pentose derived from ribose.
Flavin nucleotides are:
FMN: Flavin mononucleotide, riboflavin is attached to a phosphate group.
FAD: Flavin adenine dinucleotide, is formed by an FMN molecule linked to another AMP molecule through a diester bond.
Both act as coenzymes of dehydrogenases in oxidation-reduction reactions. The oxidized forms, FAD and FMN, are responsible for accepting electrons and protons and are reduced to FADH2 and FMNH2. They participate in the Krebs cycle or the respiratory chain.
Coenzyme A
It is made up of ADP, pantothenic acid (vitamin B5) and a short ethylamine chain linked to a thiol group (β-mercaptoethylamine). It is responsible for intervening in the enzymatic reactions involved in cellular metabolism, acting as a transporter of acyl groups that come from organic fatty acids.
