An introduction to nucleotides

What are nucleotides and what do they do?

 

The simple answer

The most basic genetic material found in the nucleus of any cell is DNA which forms the blueprint of all life. Nucleotides are the key structural components that form the basis of that DNA. This is why nucleotides are often referred to as the “building blocks of life”.

In its most familiar form, in DNA’s double helix structure, pairs of nucleotides are loosely bonded together to form the “steps” of the DNA “spiral staircase”.

 

The scientific answer

Nucleotides are organic compounds that form the basic building blocks of nucleic acids (information-containing molecules), such as DNA and RNA. Nucleotides consist of a nitrogen-containing base, a pentose sugar and one to three phosphate groups. The DNA molecule consists of nucleotides in which the sugar component is deoxyribose and the RNA molecule consists of nucleotides in which the sugar is a ribose.

The most common nucleotides are divided into two groups, called “purines” (double-ringed structures) and “pyrimidines” (single-ringed structures), based on the construction of their nitrogenous bases.

In DNA, the purine bases include adenine (A) and guanine (G) while the pyrimidine bases are thymine (T) and cytosine (C). RNA includes adenine, guanine, cytosine, and uracil (U) instead of thymine (thymine is produced when a methyl is added to uracil).

The molecular structure of DNA as described by Watson and Crick, in Cambridge in 1953, has not changed too much. However our full understanding of the importance of its constituent parts, and particularly the role of nucleotides in our diet, has only recently come to light.

 

NNNXL – The structure of DNA

 

figure 1: In its most familiar form, in DNA’s double helix structure, pairs of nucleotides are loosely bonded together to form the “steps” of the DNA “spiral staircase”.

 

The nucleotide “base pairs”

The outside spine of a DNA strand is made up of the sugar and phosphate portions of the nucleotides, while the middle parts (the rungs or steps) are made of complementary pairs of the nitrogenous bases – purine with pyrimidine (G with C, A with T) – and held together by weak hydrogen bonds. It is this hydrogen bond between phosphates that gives the DNA strand its characteristic twist (see figure 1).

This base pairing at the heart of the DNA structure means it lends itself extremely well to replication. The beauty of this structure is that it can unzip down the middle and each side can serve as a pattern or template for the other side (see Cell regeneration).

However the availability and variety of ready-to-use nucleotide raw material is vital for this process.

NNNXL – Nucleotides found in DNA

 

figure 2: The most common nucleotides are divided into two groups, called “purines” (double-ringed structures) and “pyrimidines” (single-ringed structures), based on the construction of their nitrogenous bases. In DNA, the purine bases include adenine (A) and guanine (G) while the pyrimidine bases are thymine (T) and cytosine (C).

 

NNNXL – Nucleotides found in RNA

 

figure 3: RNA includes adenine, guanine, cytosine, and uracil (U) instead of thymine (thymine is produced when a methyl is added to uracil).

 

What are the main functions of nucleotides?

As well as their function as the “building blocks of life”, in forming the structure of DNA and RNA, nucleotides are also involved in almost all the activities of each cell. In particular, nucleotides are essential for the transfer of energy, the production of protein and the mediation of hormone signals.
Cells in the body which have a large turnover rate have a higher nucleotide requirement. These include: white blood cells (immune cells formed in the bone marrow); cells in the wall of the small intestine; and “good” gut microflora; making the body dependent on a supply of nucleotides to serve both the digestive and immune systems.

This information is taken from our ground-breaking publication, “Putting you completely in the picture” – an introduction to nucleotides.