A nucleotide is much like a plastic bead. On its
own, it might not look like or do much. But pair it together with beads of complementary colors,
shapes, and sizes, and you’ve got a jewelry masterpiece! In this video, we’re going to find
out what nucleotides are and what their function is. Now, let’s first answer the question… What is
a nucleotide? Nucleotides are molecules that make up nucleic acids, clicking and clacking together
to form DNA and RNA. Nucleotides are made of three main components: a 5-carbon sugar molecule
(ribose for RNA, and deoxyribose for DNA); the other 2 components of nucleotides are a
phosphate group, and a nitrogenous base called a nucleobase. Nucleic acids are composed
of nucleotide chains, linked by 3’ and 5’ phosphodiester linkages. A phosphodiester linkage,
or bond, you can also call it bond, combines the phosphate group and the hydroxyl group of two
sugars through a condensation reaction. The 3rd carbon of one sugar joins with the 5th carbon
of another… and voila! A 3’ and 5’ phosphodiester linkage. There are 5 nucleobases that make up
nucleotides and pair together to form DNA or RNA. You have adenine (A), cytosine (C), guanine
(G), thymine (T) and uracil (U), and they group together in complementary ways to form nucleic
acids. In DNA, adenine and thymine (A-T) group together, and cytosine and guanine (C-G) group
together. In RNA, uracil replaces thymine, so the group pairings change to adenine and
uracil (A-U) and cytosine and guanine (C-G). These nitrogenous base pairings are non-negotiables
in the world of nucleotides, believe me. You’ll never see an A-G or a C-U pairing; what you see
here is what you get! Based on the structure of the nitrogenous base, nucleotides can also
be further divided into purine bases (which are our friends adenine and guanine), and
pyrimidine bases (that include thymine, uracil, cytosine). Purine bases have two carbon
rings, a pyrimidine ring and an imidazole ring, with four nitrogen atoms in the whole structure.
Pyrimidine bases just have one pyrimidine ring, with only two nitrogen atoms in the structure.
These purine and pyrimidine structures — composed of Adenine, Guanine, Thymine or Uracil, and
Cytosine — are called “primary” or “canonical,” considered “fundamental units of the genetic
code!” Okay, so now we know what a nucleotide is, but what does it do? Well, nucleotides are the
building blocks for nucleic acids, but they’re capable of so much more! The little jewelry beads
that are nucleotides also carry energy in the form of Adenosine Triphosphate (or ATP), giving energy
to different intercellular activities including protein synthesis, amino acid synthesis, and more!
They also act as cofactors in cellular signaling, contribute to regulating metabolic function, and
send chemical signals to different cells… lots of capability for a tiny plastic bead,
right? Speaking of DNA and nucleotides, click on the next video on our screen to learn
more about the fascinating structure and functions of DNA. And like the video, so you tell me and
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