Introduction

Nucleotides are very important biological molecules which provide the basis for genetic inheritance and for powering the billions of chemical reactions that occur in the body on a daily basis.  In this activity, we will explore the structure of nucleotides in biological systems.

Learning

Nucleotides all share a common chemical structure consisting of three components: a nitrogenous base, a pentose (five-carbon) sugar, and a phosphate group. Each nitrogenous base in a nucleotide is attached to a sugar molecule, which is attached to one or more phosphate groups.

When combined they form the following structure:

Nucleotides combined direct cellular activities such as cellular division and protein assembly. There are two types of nucleic acids, DNA and RNA.

DNA

DNA (deoxyribonucleic acid) is located in the nucleus of a cell and is the genetic blueprint that directs how cells work. It contains the directions on the manufacture of all the proteins that control cellular functions. It is a twisted structure called a helix and is composed of four subunits called nucleotides. Each nucleotide is made of a deoxyribose (pentose) sugar, a phosphate group and a nitrogenous base. There are four different bases that make the four subunits. If the twisted structure is unwound it resembles a ladder, with the rungs of the ladder composed of two bases bonded together by hydrogen bonds. The sides of the ladder is made of the sugar and phosphate groups. The bases have distinct bonding rules. Adenine is always bonded with thymine and guanine is always bonded with cytosine.

RNA

RNA (ribonucleic acid) is involved in protein synthesis. RNA is a single strand made of four subunits. A pentose sugar (ribose), a phosphate group and four nitrogenous bases, Adenine, Uracil, Cytosine, and Guanine.

There are four types of RNA.

• Messenger RNA (mRNA) – this carries the genetic message from the DNA located in the nucleus to the ribosomes located in the cytoplasm. Called transcription.
• Ribosomal RNA (rRNA) – this makes sure the mRNA is positioned correctly on the ribosome.
• Transfer RNA (tRNA) – this allows the correct amino acid to be placed in the polypeptide sequence made at the ribosome.
• MicroRNA (miRNA) – helps insure the correct sequence of amino acids are being assembled

Summary

In this lesson, you have learned that:

• Nucleotides are the subunits or building blocks of larger Nucleic Acid molecules
• Nucleotides consist of a central 5-Carbon sugar molecule (ribose or deoxyribose), a Phosphate Functional Group, and a Nitrogen/Carbon containing base.
• For DNA, the 4 bases are:
• Adenine
• Thymine
• Cytosine
• Guanine
• For RNA, the 4 bases are:
• Adenine
• Uracil
• Cytosine
• Guanine

 Sources:

Cornell, B. 2016. BioChain. [ONLINE] Available at: http://ib.bioninja.com.au. Accessed May 3, 2021.

“Nucleic Acids.” By OpenStax Biology 2e. Retrieved from: https://openstax.org/books/biology-2e/pages/3-5-nucleic-acids/ Licensed under: CC-BY: Attribution

Nucleic Acids. (2021, March 6). Retrieved May 21, 2021, from https://bio.libretexts.org/@go/page/1792