In nucleic acid chemistry, which combination of components correctly describes the structure of a typical nucleotide in DNA or RNA?

Introduction / Context:
Nucleotides are the basic building blocks of nucleic acids such as DNA and RNA. Understanding their structure is essential for grasping how genetic information is stored and transmitted. The original statement “Nucleotides are made of a pentose only” is incomplete and misleading, so this question rebuilds it into a clearer definition task. You are asked to identify the full set of components that together make up a nucleotide.

Given Data / Assumptions:

• The question refers to nucleotides in DNA and RNA.
• Options list different combinations of sugars, bases, phosphate, and other components.
• We assume knowledge that DNA and RNA are polymers of nucleotides.

Concept / Approach:
A nucleotide has three key parts: 1) A pentose sugar (deoxyribose in DNA or ribose in RNA). 2) A nitrogenous base (adenine, thymine, guanine, cytosine, or uracil). 3) One or more phosphate groups attached to the sugar. The sugar and base together form a nucleoside; adding the phosphate group converts a nucleoside into a nucleotide. Any description that leaves out the base or phosphate is incomplete. Sugars used in nucleotides are typically five carbon pentoses, not six carbon hexoses.

Step-by-Step Solution:
Step 1: Recall that nucleotides in DNA and RNA always contain a pentose sugar, either deoxyribose or ribose. Step 2: Remember that each nucleotide also has a nitrogenous base attached to the sugar, forming a nucleoside part. Step 3: Know that a phosphate group is attached to the sugar, allowing nucleotides to link together in long chains via sugar phosphate backbones. Step 4: Select the option that includes all three components: pentose sugar, nitrogenous base, and phosphate group.

Verification / Alternative check:
Textbook diagrams of DNA and RNA clearly show each nucleotide as consisting of a sugar, a phosphate, and a base. The sugar phosphate backbone forms the outer framework of the double helix, while the bases project inward and pair with complementary bases. Chemical structures of adenosine triphosphate, a nucleotide, also show this tri component structure. These consistent representations confirm that all three parts are required for a complete nucleotide.

Why Other Options Are Wrong:

• A pentose sugar only: This describes just one component. Without base and phosphate, it is not a nucleotide.
• A nitrogenous base and phosphate only: This combination lacks the sugar and is not the correct structural description of a nucleotide.
• A hexose sugar, a fatty acid, and a phosphate: This more closely resembles components of lipids or phospholipids, not nucleotides, and uses a six carbon sugar rather than a pentose.

Common Pitfalls:
Learners sometimes confuse the terms nucleoside and nucleotide. A nucleoside consists of just the sugar and base, while a nucleotide also includes one or more phosphate groups. Another common error is to forget that the sugar in DNA and RNA is a pentose, not a hexose like glucose. Keeping these distinctions clear helps avoid mistakes in questions on nucleic acid structure.

Final Answer:
A typical nucleotide in DNA or RNA consists of a pentose sugar, a nitrogenous base, and a phosphate group.