Is Adenine Sugar: Why, How, What Type, Detailed facts

Adenine is a nine membered cyclic purine nucleobase, not a sugar.

Adenine is made up of two separate cyclic molecules fused to each other via an edge (a six-membered pyrimidine ring and a five-membered imidazole ring). Also unlike sugars or carbohydrates Nitrogen is a major component of adenine influencing its chemical properties.

So if asked “Is adenine sugar?” the answer would simply be no. Adenine is closely associated with sugars in the form of ribose and deoxyribose in DNA, RNA, AMP, ADP and ATP. But Adenine in itself is far from being a sugar itself.

Why is adenine sugar?

In biological terms or explanations, Adenine can never be called sugar or carbohydrate.

Carbohydrates or simple sugars are composed of 3 main components- Oxygen, Hydrogen and Oxygen. Whereas Nitrogen is a major component of nucleobases like Adenine.

Carbohydrates or sugars, in general, have a neutral chemical composition and nature. On the other hand, adenine is a nitrogenous base as is found to be an H+  or proton donor.

How is adenine sugar?

Adenine is not considered a sugar or sugar derivative chemically.

Adenine is a purine nitrogenous base molecule found in nucleic acids and some other biomolecules. In most of these structures, we find adenine attached to other sugars.

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Simple pyrimidine structure of Adenine
Image: Wikipedia

Carbon, Hydrogen and Oxygen atoms are the main components in sugar or carbohydrate structures, sometimes having substitutes side chains. They usually occur in cyclic structures and mainly five-membered or six-membered ringed monomers joined together.

Usually, they are chemically neutral unlike nitrogenous bases like Adenine. Adenine is more complex due to the presence of a six-membered pyrimidine ring fused to an imidazole ring that is made up of five atoms. The final structure is a nine membered complex molecule.

What sugar is in adenine?

Adenine is a purine base, not a sugar or carbohydrate.

Adenine is a nitrogenous purine(nine membered ring structure) base. It is a part of nucleic acids like DNA and RNA, but it’s not an acid in and of itself.

Adenine is closely associated with sugars like – deoxyribose and ribose. DNA and RNA nucleotides also contain adenine, along with the phosphates Adenosine Monophosphate (AMP), Adenosine Diphosphate (ADP), and Adenosine Triphosphate (ATP).

Another proof that adenine is not a sugar, is that we cannot salvage sugar or other carbohydrates to obtain adenine via the salvage pathway of nucleotide synthesis. Nucleotides can only be produced from the breakdown of amino acids.

Is adenine a deoxyribose sugar?

Biologically classified Adenine is a cyclic nitrogenous base.

Adenine is present in both DNA and RNA and can be attached to both ribose and deoxyribose. But Adenine in itself is a nine membered cyclic molecule.

A nucleotide containing adenine is one of the nitrogenous bases found in DNA. A DNA nucleotide is composed of three parts: a nitrogenous base (such as Adenine, Guanine, Thymine or Cytosine), a sugar molecule called deoxyribose and a phosphate group. Adenine, Guanine, Thymine, or Cytosine are examples of nitrogenous bases.

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DNA nucleotide containing Adenine
Image: Wikipedia

These nitrogenous bases are what allow the 2 antiparallel DNA strands to bond and form the double helix structure. Hence Adenine is not a deoxyribose sugar but attached to it in a DNA nucleotide.

What sugar is found in Flavin Adenine Dinucleotide (FAD)?

Flavin Adenine Dinucleotide or FAD structure technically possesses only one sugar molecule, a ribose.

One FAD molecule is made up of two parts- an adenine nucleotide or adenine monophosphate(AMP) joined with a Flavin mononucleotide-(FMN) or riboflavin-5’-phosphate, via their phosphate groups.

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Structure of FAD
Image: Wikipedia

The AMP is made up of one Adenine, a ribose sugar and a phosphate group forming a typical mononucleotide molecule also seen in RNA. While riboflavin-5′-phosphate is a molecule derived from Vitamin B2 or Riboflavin under the effect of an enzyme called riboflavin kinase.

So the only sugar found in the structure of FAD is a ribose.

When adenine is attached to a ribose sugar?

Adenine can be found attached to ribose sugar in – RNA nucleotide, AMP, ADP and ATP.

Adenine is a key integrant of all nucleic acids, and it binds to Thymine and Uracil, in DNA and RNA respectively. Adenine is also one of the constituents of Adenosine Triphosphate, which serves as the cellular energy currency.

The nucleotide for RNA has 3 parts:

  • A sugar which in the case of  RNA is ribose
  • A nitrogenous base- Adenine, Uracil, Guanine or Cytosine and
  • A phosphate group

So adenine can be found attached to ribose in the RNA nucleotides.Also in molecules like Adenosine Monophosphate (AMP), Adenosine Diphosphate (ADP) and Adenosine Triphosphate (ATP), we see that Adenine is attached to a ribose sugar and one, two or three phosphate groups respectively.

AMP is in itself an RNA nucleotide, while ADP and ATP are important energy suppliers in biological cells. They can act as catalyzers or enzymes and provide energy themselves or help process other reactions.

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Structure of Adenosine Triphosphate or ATP
Image: Wikipedia

Hence in the above biomolecules, we can find Adenine attached to ribose sugars naturally.

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