A nucleoside differs from a nucleotide. It lacks the

Options

A. base
B. sugar
C. phosphate group
D. hydroxyl group

Answer

To solve the question "A nucleoside differs from a nucleotide. It lacks the", we need to understand the structural differences between nucleosides and nucleotides.

### Step-by-Step Solution:

1. **Define Nucleosides and Nucleotides**:
- A **nucleoside** consists of two components: a nitrogenous base (adenine, guanine, cytosine, thymine, or uracil) and a pentose sugar (ribose or deoxyribose).
- A **nucleotide** is similar to a nucleoside but includes an additional component: a phosphate group.

2. **Identify Components**:
- Both nucleosides and nucleotides contain:
- A nitrogenous base
- A pentose sugar
- The key difference is that nucleotides have a phosphate group attached to the sugar.

3. **Analyze the Options**:
- **Base**: Present in both nucleosides and nucleotides. (Incorrect)
- **Sugar**: Present in both nucleosides and nucleotides. (Incorrect)
- **Phosphate group**: Absent in nucleosides but present in nucleotides. (Correct)
- **Hydroxyl group**: Present in the sugar component of both nucleosides and nucleotides. (Incorrect)

4. **Conclusion**:
- The correct answer is that a nucleoside lacks the **phosphate group**, which is present in a nucleotide.

### Final Answer:
A nucleoside differs from a nucleotide because it lacks the **phosphate group**.

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