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Nucleic acids constitute the genetic material present in all living systems. They are of two types:

  1. Deoxyribose nucleic acid (DNA)
  2. Ribose nucleic acid (RNA)

The nucleic acids are composed of 3 important chemical components:

  1. Sugar: It is a pentose sugar (5 carbon atoms) having a pentagonal ring structure. It is Deoxyribose sugar in DNA while in RNA it is Ribose sugar.
  2. Phosphate: It is present as Phosphoric acid (H3PO4).
  3. Nitrogen Bases: Based on their chemical structure they are grouped into 2 classes:
    1. Purines which include Adenine (A) and Guanine (G) and
    2. Pyrimidines which include Cytosine (C), Thymine (T) and Uracil (U).

In DNA, Thymine is present while in RNA Thymine is replace by Uracil. The base pairing of the nitrogen bases are specific. Adenine (A) pairs with Thymine (T) in DNA while in RNA it pairs with Uracil (U) and Cytosine (C) pairs with Guanine (G)

Nucleic acids are long chain molecules formed of several repeating units called Nucleotides

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