Question

Given below are two statements: 

Statement I: A unit formed by the attachment of a base to 1' position of sugar is known as nucleoside.

Statement II: When nucleoside is linked to phosphorous acid at 5 -position of sugar moiety, we get neucleotide. 

In the light of the above statements, choose the correct answer from the options given below:

• A. Both Statement I and Statement II are false
• B. Statement I 1s true but Statement II is false
• C. Statement I is false but Statement II is true
• D. Both Statement I and Statement II are true

Answer 1

The Correct Option is B

Let's analyze the given statements regarding nucleosides and nucleotides:

1. Statement I: A unit formed by the attachment of a base to 1' position of sugar is known as nucleoside.
2. Statement II: When nucleoside is linked to phosphorous acid at 5-position of sugar moiety, we get nucleotide.

Explanation:

1. Understanding Statement I:
   • Nucleosides are indeed formed by attaching a nitrogenous base (either a purine or pyrimidine) to a pentose sugar (ribose in RNA and deoxyribose in DNA) at the 1' carbon position of the sugar.
   • This statement is consistent with biochemical nomenclature and is, therefore, correct.
2. Understanding Statement II:
   • A nucleotide consists of three components: a nitrogenous base, a pentose sugar, and one or more phosphate groups.
   • In a nucleotide, a phosphate group is bonded to the 5' carbon of the pentose sugar, but this is not described as linking to "phosphorous acid". The term "phosphorous acid" is incorrect in this context as nucleotides contain phosphate groups rather than phosphorous acid.
   • Hence, this statement contains a factual inaccuracy.

Based on these explanations:

• Statement I is true since it correctly describes a nucleoside.
• Statement II is false due to incorrect terminology regarding the phosphate group.

Conclusion: The correct answer is "Statement I is true but Statement II is false."