Lesson 13: Nucleic Acids

🧬 What Are Nucleic Acids?

Nucleic acids are large molecules made up of smaller units called nucleotides.
You can think of nucleic acids as “chains” made from “links” (the nucleotides).

Nucleic acids have two main types:

  • DNA (Deoxyribonucleic acid)
  • RNA (Ribonucleic acid)

Both DNA and RNA are essential for storing genetic information and making proteins in living cells.

🧪 Where Are Nucleic Acids Found?

  • DNA: It is mostly found in the chromosomes of the nucleus of cells, but there are also small amounts in mitochondria (the cell’s powerhouses) and chloroplasts (in plant cells).
  • RNA: It is found in the nucleolus (a structure in the nucleus), ribosomes (the “factories” for protein production), and cytosol (the liquid part of the cell).

🔬 What Makes Up a Nucleoside?

A nucleoside is made of:

  • A nitrogen base: This is a molecule that contains nitrogen and is involved in storing genetic information.
  • A pentose sugar: This is a type of sugar with five carbon atoms (hence the name “pentose”).

In simple terms:
Think of a nucleoside like a bike:

  • The nitrogen base is like the seat, and the pentose sugar is like the frame. Together, they make the whole “bike.”

🧩 Components of a Nucleotide

A nucleotide is a nucleoside with a phosphate group added to it.
Let’s break down each component:

  1. Pentose Sugars:
    • RNA contains ribose, a sugar with one oxygen atom more than deoxyribose.
    • DNA contains deoxyribose, which is ribose without one oxygen atom.
      Think of ribose and deoxyribose like two versions of a toy car—one is fully equipped with all parts (ribose), while the other is missing a small part (deoxyribose).
  2. Nitrogenous Bases:
    There are two main types of nitrogen bases:
    • Pyrimidine Bases:
      These are single-ringed nitrogen bases.
      • Cytosine (C) is found in both DNA and RNA.
      • Thymine (T) is only found in DNA.
      • Uracil (U) is only found in RNA.
        Mnemonic: Think of the word “CUT” to remember Cytosine, Uracil, and Thymine.
    • Purine Bases:
      These are double-ringed nitrogen bases.
      • Adenine (A) is found in both DNA and RNA.
      • Guanine (G) is found in both DNA and RNA.
        Mnemonic: To remember these, think of the letters “AG”, which stands for Adenine and Guanine.
  3. Phosphoric Acid:
    This is a molecule that links nucleotides together.
    • The phosphate group attaches to the 5′ carbon of the pentose sugar.
    • This creates a nucleotide, which forms a long polynucleotide chain.
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