Understanding RNA Nucleotides

A nucleotide is the basic building block of nucleic acids like RNA and DNA. It consists of three components:

1. A nitrogenous base
2. A pentose sugar
3. A phosphate group

Step 1: Identify the Correct Nitrogenous Bases for RNA

RNA uses four nitrogenous bases:

• Adenine (A)
• Guanine (G)
• Cytosine (C)
• Uracil (U)

DNA uses Thymine (T) instead of Uracil. Therefore, any option containing Thymine is incorrect for an RNA nucleotide.

Step 2: Identify the Correct Sugar for RNA

The pentose sugar in RNA is Ribose. DNA uses Deoxyribose. Therefore, any option containing Deoxyribose is incorrect for an RNA nucleotide.

The chemical formula for Ribose is $C_5{H}_{10}{O}_5$.

Step 3: Analyze Each Option

Let's evaluate the given choices one by one:

Option 1: Adenine + deoxyribose + phosphate
Base (Adenine) is valid for RNA, but the sugar (deoxyribose) is for DNA. This is incorrect.

Option 2: Uracil + ribose + phosphate
Base (Uracil) is exclusive to RNA. Sugar (Ribose) is correct for RNA. Phosphate is common to both. This is the correct combination.

Option 3: Thymine + ribose + phosphate
Base (Thymine) is used only in DNA, not RNA. The sugar is correct, but the wrong base makes this incorrect.

Option 4: Guanine + deoxyribose + phosphate
Base (Guanine) is valid for both RNA and DNA, but the sugar (deoxyribose) is for DNA. This is incorrect.

Final Answer

The correct combination that can form a nucleotide of RNA is: Uracil + ribose + phosphate.

Related Topics & Formulae

Structure of a Nucleotide

The general structure of a nucleotide can be represented by the formation of an N-glycosidic bond between the sugar and the base, and an ester bond between the sugar and the phosphate.

The condensation reaction to form the sugar-phosphate backbone is crucial for polymer formation.

Key Differences Between RNA and DNA