Question

Which of the following are constituent components of deoxyribo nucleosides
(A) Adenine base
(B) Ribose sugar
(C) Thyamine base
(D) Uracil base
Choose the correct answer from the options given below:

• A. (A) and (B) only.
• B. (A) and (C) only.
• C. (A) and (D) only.
• D. (B), (C) and (D) only.

Hint:

To remember the building blocks:
- Nucleoside = Sugar + Base.
- Nucleotide = Sugar + Base + Phosphate.
- Deoxy- implies deoxyribose sugar and excludes Uracil (which belongs to ribose-containing RNA).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Nucleosides are compounds consisting of a nitrogenous base covalently linked to a pentose sugar (ribose or deoxyribose) via a \(\beta\)-N-glycosidic bond.
Depending on the sugar and the bases present, they are classified as ribonucleosides or deoxyribonucleosides.

Step 2: Detailed Explanation:
Let us analyze the constituent components of a deoxyribonucleoside:
- Pentose Sugar: A deoxyribonucleoside must contain 2-deoxyribose as its sugar component.
Ribose sugar (B) is only present in ribonucleosides (found in RNA).
- Nitrogenous Bases: The bases present in deoxyribonucleosides are those found in DNA.
These are Adenine (A), Guanine, Cytosine, and Thymine (C).
Uracil base (D) is found almost exclusively in ribonucleosides of RNA.
Therefore:
- Adenine base (A) can combine with deoxyribose to form deoxyadenosine (a deoxyribonucleoside).
- Thymine base (C) (spelled "Thyamine" in the question paper) can combine with deoxyribose to form deoxythymidine (a deoxyribonucleoside).
Thus, only (A) and (C) are constituent components of deoxyribonucleosides.

Step 3: Final Answer:
The constituent components of deoxyribonucleosides among the choices are (A) and (C) only.