Nucleic Acids and Their Functions

Nucleic Acid Structure and Function

• Nucleic acids are polymers of nucleotides linked by phosphodiester bonds. Their primary function is to store and express genetic information.
• There are two types of nucleic acids: Ribonucleic acid (RNA) and Deoxyribonucleic acid (DNA).
• Nucleic acids are made up of Nucleotides.

Nucleotides and Nucleosides

• A nucleotide is composed of a nitrogenous base linked to a pentose sugar, with a phosphate group attached.
• A nucleoside is composed of a nitrogenous base linked to a pentose sugar.
• Nucleotides can be broken down into: Nucleoside + Phosphate group.

Nitrogenous Bases

• There are two families of nitrogenous bases: Purines and Pyrimidines.
• Purine bases include Adenine (A) and Guanine (G).
• Pyrimidine bases include Cytosine (C), Thymine (T) and Uracil (U).

Pentose Sugars

• There are two types of pentose sugars:
  • Ribose (present in RNA).
  • Deoxyribose (present in DNA). Deoxyribose is a modified form of ribose, where an oxygen atom has been removed from carbon 2.

Phosphate Group

• The phosphate group (H3PO4) attaches to carbon 5 of the ribose sugar through an ester bond.

Nucleic Acids Structure and Nomenclature

• In nucleotides and nucleosides, the nitrogenous base is linked to the C1 of the sugar by an N-glycosidic bond.
• Nucleotides are named based on their nucleoside base and the number of Phosphate groups attached.
  • For example, Adenosine monophosphate (AMP) is composed of Adenosine (NB) and one phosphate group.

Biological Importance of Nucleotides and Nucleosides

• Building blocks of nucleic acids (DNA and RNA).
• High-energy source, like adenosine triphosphate (ATP).
• Constituents of coenzymes like Flavin adenine dinucleotide (FAD) and Nicotinamide adenine dinucleotide (NAD).
• Serve regulatory functions, like cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP).
• Synthetic nucleotide analogue drugs are used in chemotherapy.
• Pyrimidines are precursors of metabolic intermediates, like UDP-glucose and CDP-choline.

Polymerisation of Nucleotides

• Nucleotides are linked together by a 3′, 5′ phosphodiester bond.
• The 3′-OH of one nucleotide is attached to the phosphate group of the next nucleotide.
• This results in a phosphate group being attached by two ester bonds to the carbon 3’ and 5’ of two successive nucleotides.
• Enzymes called nucleases can hydrolyze these phosphodiester bonds.
• Polynucleotides have two terminals:
  • Free 3′ hydroxyl (-OH) at one end called the 3′-end.
  • Free 5′ phosphate group at the other end called the 5′-end.
• Nucleic acids have a defined polarity due to the directionality of the 3′, 5′ bond.

Explore the structure and function of nucleic acids, including DNA and RNA. This quiz covers essential topics like nucleotides, nitrogenous bases, and the role of pentose sugars. Test your knowledge on the building blocks of genetic information.