Question

A nucleoside differs from a nucleotide because it lacks:

• A. Nitrogenous base
• B. Pentose sugar
• C. Phosphate group
• D. Glycosidic bond

Hint:

Remember the relation: \[ \boxed{ \text{Nucleoside}+\text{Phosphate} = \text{Nucleotide} } \] Examples: \[ \boxed{ \begin{aligned} \text{Adenosine} &\rightarrow \text{Nucleoside}\\ \text{AMP} &\rightarrow \text{Nucleotide} \end{aligned} } \] The phosphate group is the distinguishing feature of a nucleotide.

Answer 1

The Correct Option is C

Concept: Nucleosides and nucleotides are the building blocks of nucleic acids. A nucleoside consists of: \[ \boxed{\text{Nitrogenous base}+\text{Pentose sugar}} \] A nucleotide consists of: \[ \boxed{\text{Nitrogenous base}+\text{Pentose sugar}+\text{Phosphate group}} \] Thus, a nucleotide is simply a nucleoside attached to one or more phosphate groups.

Step 1: Understand the composition of a nucleoside.
A nucleoside contains \[ \boxed{ \begin{aligned} &\text{Nitrogenous base}\\ +&\text{Pentose sugar} \end{aligned} } \] The base and sugar are joined by an \[ \boxed{\beta\text{-N-glycosidic bond}.} \]

Step 2: Understand the composition of a nucleotide.
A nucleotide contains \[ \boxed{ \begin{aligned} &\text{Nitrogenous base}\\ +&\text{Pentose sugar}\\ +&\text{Phosphate group} \end{aligned} } \] The phosphate group is attached to the sugar by a phosphoester bond.

Step 3: Identify the missing component.
The only difference between a nucleoside and a nucleotide is the presence of a phosphate group. Hence, \[ \boxed{\text{Nucleoside = Nucleotide }-\text{ Phosphate group}.} \] Therefore, \[ \boxed{\textbf{Option (C)}} \] is the correct answer.