My AP Biology Thoughts  Episode #48

Welcome to My AP Biology Thoughts podcast, my name is Pauline and I am your host for episode #48 called Unit #1 Chemistry of Life: Nucleic Acids Structure Function & Examples. Today we will be discussing an overview of nucleic acids in terms of their components, function, and examples.

Segment 1: Introduction to Nucleic Acids Structure Function & Examples 

Nucleic Acids are one of the big macromolecules necessary for life. They are complex organic substances present in living cells whose molecules consist of many nucleotides linked in a long chain. Let’s first talk about what makes up nucleic acids. Their monomers are nucleotides which are all made up of a phosphate group, a pentose sugar, and a nitrogenous base as shown in the diagram. The nitrogen atoms in the nitrogenous base are the extra element that differentiates nucleic acids from the three other macromolecules with the abbreviation CHOPN. Through a dehydration reaction, nucleotides link together with a phosphodiester linkage which is between the sugar and phosphate groups. The drawing shows a water molecule taken out to form this a covalent bond. The nucleotides bonded together make up the polymers of nucleic acids which are DNA and RNA.

Segment 2: Example of Nucleic Acids Structure Function

DNA and RNA are the main two examples of nucleic acids. There are major differences as well as similarities between DNA and RNA that are important to know. DNA, also known as deoxyribonucleic acid, is made up of the deoxyribose sugar, is double stranded and arranged in an antiparallel pattern. DNA is always found in the nucleus of eukaryotic cells and contains information for thousands of proteins. Its bases are cytosine, guanine, adenine, and thymine. On the other hand, RNA uses all of these bases except thymine is replaced by uracil. RNA is also only single stranded and contains information for only one protein as it leaves the nucleus after formation. They are similar in their directionality and bonding. Their nucleotides are all linked by covalent bonds and have a 3’ to 5’ directionality. The linear sequence of nucleotides have ends, defined by the 3’ hydroxyl and 5’ phosphates of the sugar in the nucleotide. During DNA and RNA synthesis, nucleotides are added to the 3’ end of the growing strand, resulting in the formation of a covalent bond between nucleotides. 

Since DNA is structured as an antiparallel double helix, each strand runs in the opposite 5’ to 3’ orientation. This means that adenine nucleotides pair with thymine nucleotides via two hydrogen bonds. Cytosine nucleotides pair with guanine nucleotides by three hydrogen bonds. This is all shown in this diagram where the black boxes are where another nucleotide would be added, and there are more hydrogen bonds highlighted in pink between Guanine and cytosine because of the antiparallel double helix. 

Segment 3: Digging Deeper Nucleic Acids Structure Function & Examples

Nucleic acids fit in the greater picture of the unit called Chemistry of Life because of their functions. As mentioned before, they carry information for making proteins which brings back the topic of the central dogma. Through transcription, the information in a strand of DNA is copied into a new molecule of messenger RNA, which is then decoded during the process of translation to build a polypeptide. Humans cannot survive without all nine essential amino acids found in proteins, so...