Nucleic Acids

Nucleic Acids

Just like the three other biological moleculesGroups of atoms bonded together., carbohydrates lipidsOrganic molecules including fats, oils, and steroids. and proteinsLarge molecules made of amino acids with various functions in the body., nucleic acids are polymersLarge molecules made of repeating monomer units. of smaller subunits called nucleotidesThe building blocks of nucleic acids.. I like this Lego analogy here. Each Lego is a nucleotideThe basic building block of DNA and RNA, consisting of a sugar, phosphate group, and nitrogenous b. However, these nucleotides are slightly different than each other. Each nucleotide or each Lego building block contains three components. It has a sugar, a phosphate group, and something called a nitrogenous baseA component of nucleotides that includes adenine, guanine, cytosine, thymine (DNA), and uracil (RNA). It is the nitrogenous baseA substance that accepts hydrogen ions (H⁺) or releases hydroxide ions (OH⁻). that gives these subunits their own identity. DNA is actually two polymers of nucleotides. They are bound together by hydrogen bondsWeak attractions between hydrogen and electronegative atoms like oxygen or nitrogen., which complicates things a bit.

Nucleic Acids

The two main nucleic acids are DNA or deoxyribonucleic acidA substance that releases hydrogen ions (H⁺) in solution. and RNA which is ribonucleic acid. The difference between these two molecules is 1 oxygen atomThe smallest units of matter that retain the properties of an element. which is why DNA has the name of deoxy. As mentioned before in another mini lecture I have taught from books that consider ATPThe energy currency of cells used for muscle contraction. to be a nucleic acid. I don’t necessarily disagree with that. Made ATP is technically made from a sugar a bunch of phosphate and a modified nitrogenous base. So, I accept.

DNA really has one purpose in your body. DNA is like an encyclopedia. Or, I guess it’s better like a recipe book. It holds all of the recipes for all of the proteins that you might wanna make.  DNA also holds the instructions for making more cellsThe basic structural and functional units of life.. So DNA is a storage molecule basically. It stores information that dictates the sequence of the nucleotides or Lego blocks.

Conversely RNA has more than a few functions and we are discovering more of those functions all the time. Let’s talk about DNA then RNA.

DNA Structure

Let’s go back to our analogy with the legos for a moment. We have one molecule of DNA with 2 strands of nucleotides that are bonded together by hydrogen bond. You can see this on the picture on the far left of this slide. Let’s extend that analogy and think of a ladder.  The rails of the ladder consist of the sugars. These sugars come from each nucleotide. The phosphates also come from each nucleotide. The rungs of the ladder are made up of bonded nitrogenous bases. This is where you would put your feet. Because of how the strands bond specifically, the structure does not stay as a ladder. It starts to twist into what is called a double Helix.  The picture on the right shows you with commonly called the ribbon model of DNA.  Note how the rails of the ladder are blue and yellow showing you the alternating sugar phosphate backbone. And note how the rungs of the ladder are the they nitrogenous base is paired with hydrogen bond. Why the hydrogen bonds?  They are weak.  This makes the DNA easy to break apart and reform in order to duplicate it or make proteins from it.

RNA Function

RNA can be used as a storage molecule but RNA is disposable so that’s not for long term storage. When it serves this purpose, we call it mRNA because it is a messenger.  mRNA is used to move information from the nucleusThe control center of the cell that contains DNA and directs cellular activities. to places in the cytoplasmThe gel-like substance within a cell that contains organelles and cytosol..  RNA also serves as a translationThe process of converting mRNA into a protein. molecule acting somewhat like a language to language dictionary or a decoder ring.  tRNA or transfer RNA has areas on it that can bind with mRNA and with amino acidThe building blocks of proteins, consisting of an amino group, carboxyl group, and side chain..  So it’s like tRNA knows the language of amino acids and the language of nucleotides.  In that way, it can serve as a decoder ring.  The last type of RNA that we cover in this class is rRNA(ribosomal RNA) – RNA that forms part of the ribosome and helps in protein synthesis.. It makes up a component of cells called a ribosome.  A ribosome is like a protein factory.  It takes the individual amino acids, with the help of tRNA and mRNA, and builds a specific protein. The recipe for this protein is encoded in your DNA.