NUCLEOTIDES

NUCLEOTIDES

The nucleotides that are the building blocks of nucleic acids are formed by adding a phosphate group to a nucleoside.



Nucleotides containing ribose are known as ribonucleotides, and those containing deoxyribose are known as deoxyribonucleotides.

To summarize the structural differences between DNA and RNA:

DNA (deoxyribonucleic acid)

• Sugar is deoxyribose
• DNA is a polymer of deoxyribonucleotides
• Bases are adenine, guanine, cytosine and thymine

RNA (ribonucleic acid)

• Sugar is ribose
• RNA is a polymer of ribonucleotides.
• Bases are adenine, guanine, cytosine and uracil (instead of thymine)

NUCLEOSIDES

NUCLEOSIDES

Both DNA and RNA contain nucleotides with similar components. In RNA, the sugar component is ribose, as indicated by the name "ribonucleic acid". In DNA, or deoxyribonucleic acid, the sugar component is deoxyribose. The prefix deoxy means that an oxygen atom is missing from one of the ribose Carbon atoms.

When a sugar bonds together with a Nitrogen base, you now have two of the three components of a nucleotide. This structure is known as a nucleoside.

There are FIVE Nitrogen bases that are found in DNA and RNA (although Uracil is found ONLY in RNA!). These five bases are divided into two categories based on their molecular structure. Click onto the hyperlinks and look at the structures below to see if you can tell what differentiates each category!

1 purines (Adenine and Guanine)
2 pyrimidines (Thymine, Cytosine, and Uracil)



You should notice that the purines have two ring structures while pyrimidines have only one ring structure. The way I've always remembered the difference is that the LONGER word (pyrimidine) represents the SMALLER structure (only one ring), and vice-versa!

COMPOSITION OF NUCLEIC ACIDS

COMPOSITION OF NUCLEIC ACIDS

This section of the tutorial begins to look at the composition of nucleic acids starting from the biggest subunit and going all the way down to the very chemical elements that make them up.

Nucleic acids are one of several macromolecules in the body in addition to fats, proteins and carbohydrates. So it isn't surprising that nucleic acids are built like these other macromolecules. Nucleic acids and the other macromolecules just mentioned are polymers made up of individual molecules linked together in long chains.

• Proteins are polypeptides made up of individual amino acids linked together,
• Carbohydrates are polysaccharides made up of individual monosaccharides linked together, and
• Nucleic acids are polynucleotides made up of individual nucleotides linked together.

If you go even further, a nucleotide can itself be further broken down to yield three components:

• a sugar,
• a Nitrogen (amine) base, and
• phosphoric acid.
  

As mentioned in the Introduction to this tutorial, there are two types of nucleic acids: DNA and RNA. DNA stores genetic information, and RNA allows that information to be made use of in the cell. Before we discuss the overall structure of nucleic acids as polymers, we should probably find out how their individual component parts are joined together and how DNA and RNA differ.