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Nucleic Acids


Nucleic Acids: Structure & Bonding | Biology Class 11 - NEET
Chemical Composition

  •  Meischer discovered nucleic acids in nucleus of pus cell and called it ''nuclein''.
  • The name nucleic acid proposed by ''Altman''.

 Nucleic acids are polymer of nucleotides = nitrogen base + pentose + phosphate 


A. Nitrogenous Base

On the basis of structure, nitrogen bases are broadly of two types :

1.   Pyrimidines – Consist of one pyrimidine ring. Skeleton of ring composed of two nitrogen and four Carbon atoms e.g. Cytosine, Thymine and Uracil.

Nucleic Acids: Structure & Bonding | Biology Class 11 - NEET    Nucleic Acids: Structure & Bonding | Biology Class 11 - NEET    Nucleic Acids: Structure & Bonding | Biology Class 11 - NEET              


2.   Purines – Consist of two rings i.e. one pyrimidine ring (2N + 4C) and one imidazole ring (2N + 3C) e.g. Adenine and Guanine.

Nucleic Acids: Structure & Bonding | Biology Class 11 - NEET    Nucleic Acids: Structure & Bonding | Biology Class 11 - NEET                                            


B. Pentose Sugar

Nucleic Acids: Structure & Bonding | Biology Class 11 - NEET    Nucleic Acids: Structure & Bonding | Biology Class 11 - NEET    Nucleic Acids: Structure & Bonding | Biology Class 11 - NEET

Nitrogen base forms bond with first carbon of pentose sugar to form a nucleoside. Nitrogen of first place (N1)  forms bond with sugar in case of  Pyrimidines while in purines nitrogen of ninth place (N9) forms bond with sugar.


C. Phosphate

Phosphate forms ester bond (covalent bond) with fifth carbon of sugar to form a complete nucleotide.

Nucleic Acids: Structure & Bonding | Biology Class 11 - NEET

 

Types of Nucleosides and Nucleotides:

1.   Adenine + Ribose = Adenosine

      Adenosine + Phosphate = Adenylic acid

2.   Adenine + Deoxyribose = Deoxy adenosine

      Deoxy adenosine + P = Deoxy adenylic acid  

3.   Guanine + Ribose = Guanosine

      Guanosine + P =  Guanylic acid

4.   Guanine + Deoxyribose = Deoxy guanosine

      Deoxy  guanosine + P = Deoxy guanylic acid 

5.   Cytosine + Ribose  = Cytidine

      Cytidine + P = Cytidylic acid 

6.   Cytosine + Deoxyribose = Deoxycytidine

      Deoxycytidine  + P = Deoxycytidylic acid 

7.   Uracil + Ribose = Uridine

      Uridine + P = Uridylic acid    

8.   Thymine + Deoxyribose = Deoxy thymidine

      Deoxythymidine  + P = Deoxythymidylic acid

The document Nucleic Acids: Structure & Bonding | Biology Class 11 - NEET is a part of the NEET Course Biology Class 11.
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FAQs on Nucleic Acids: Structure & Bonding - Biology Class 11 - NEET

1. What are the chemical components of nucleic acids?
Ans. Nucleic acids are composed of nucleotides, which are made up of three components: a nitrogenous base (adenine, guanine, cytosine, thymine, or uracil), a pentose sugar (deoxyribose in DNA or ribose in RNA), and a phosphate group.
2. How are nucleotides bonded to form nucleic acids?
Ans. Nucleotides are bonded together through phosphodiester bonds. The phosphate group of one nucleotide is covalently bonded to the sugar group of the adjacent nucleotide, creating a backbone of alternating sugar-phosphate units.
3. What is the structure of nucleic acids?
Ans. Nucleic acids have a double-helix structure, with two polynucleotide strands running in opposite directions. The strands are held together by hydrogen bonds formed between complementary nitrogenous bases (A with T/U and G with C). The two strands are antiparallel, meaning they run in opposite directions.
4. What is the function of nucleic acids in living organisms?
Ans. Nucleic acids play a crucial role in storing and transmitting genetic information. DNA carries the genetic code necessary for the development, functioning, and reproduction of all living organisms. RNA, a type of nucleic acid, is involved in protein synthesis and gene regulation.
5. How do nucleic acids contribute to the diversity of life?
Ans. Nucleic acids are responsible for the genetic variations that exist among different organisms. Through the process of DNA replication and genetic recombination, nucleic acids enable the generation of new combinations of genetic information, leading to the diversity of traits observed in different species.
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