Relative size comparison in nucleic acid components Considering molecular structure, which of the following is the largest unit among these choices?

Introduction:
Understanding the hierarchy of nucleic acid components helps with reasoning about DNA structure, synthesis, and biochemical assays. This question asks which listed entity is structurally largest as a discrete chemical unit.

Given Data / Assumptions:

• A nucleotide is composed of a nitrogenous base, a pentose sugar, and one or more phosphates.
• A nitrogenous base alone is a single heterocyclic compound.
• A phosphate group is a small inorganic moiety.
• A carbon atom is a single element, not a molecular unit.
• Deoxyribose sugar is a component of a nucleotide but not as large as the full nucleotide.

Concept / Approach:

Compare composition. The nucleotide contains multiple components covalently linked and can carry one to three phosphates, making it the most massive unit among the options provided. All other choices are subunits or individual atoms that are incorporated into the nucleotide.

Step-by-Step Solution:

Verification / Alternative check:

Molecular weights illustrate the point. For example, dAMP has mass far exceeding either adenine alone or deoxyribose alone, and certainly larger than a phosphate group or an element such as carbon.

Why Other Options Are Wrong:

Nitrogenous base and deoxyribose represent partial components. Phosphate is a small group. A carbon atom is an element, not a macromolecular unit.

Common Pitfalls:

Confusing nucleoside with nucleotide. A nucleoside lacks phosphate and is smaller than a nucleotide, reinforcing that the nucleotide is largest among the listed units.

Final Answer:

Nucleotide