Nucleic Acids and Their Importance in Living Systems

Overview of Nucleic Acids

• Nucleic acids are one of the four essential macromolecules in living systems.
• They include DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
• DNA is the molecule responsible for carrying genetic information in living organisms; RNA also carries genetic material in some viruses.

Structure of DNA

• DNA is composed of repeating subunits called nucleotides.
• Nucleotide Components:
  • Pentose Sugar: Either ribose or deoxyribose.
  • Phosphate Group: Attached to the fifth carbon of the sugar.
  • Nitrogen Base: Attached to the first carbon of the sugar.
• DNA structure is a double helix with two strands running in opposite directions, held together by hydrogen bonds between the nitrogen bases.
• Nitrogen Bases in DNA: Adenine (A), Thymine (T), Guanine (G), Cytosine (C).
• The order of these bases constitutes the genetic code.

DNA Backbone

• Formed by phosphate-sugar bonds linking nucleotides together.
• The backbone does not carry genetic information; it supports and holds the bases.

Differences Between DNA and RNA

• Number of Strands:
  • DNA: Double-stranded.
  • RNA: Single-stranded.
• Nitrogen Bases:
  • DNA: A, T, G, C.
  • RNA: A, U (Uracil), G, C.
• Sugar Component:
  • DNA: Deoxyribose (lacks an oxygen at the second carbon).
  • RNA: Ribose (contains hydroxyl group with oxygen).

RNA Structure

• RNA is a single strand formed by the condensation of nucleotide monomers.
• The phosphate-sugar backbone is similar to that of DNA.

Base Pairing Rules

• DNA Base Pairing:
  • A pairs with T (two hydrogen bonds).
  • G pairs with C (three hydrogen bonds).
• RNA Base Pairing:
  • A pairs with U instead of T when copying DNA to RNA.

Importance of DNA

• DNA is capable of storing vast amounts of information due to the variety of possible base combinations.
• The universal nature of DNA across organisms suggests a common evolutionary ancestor.
• DNA’s small size and efficient packaging make it an ideal genetic material.