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What Makes Up Each Nucleotide in DNA RNA Biology Exam Answer
Nucleotides in nucleic acids comprise ribose/deoxyribose sugar, nitrogenous base, and phosphate—not glucose or ferrous—forming DNA/RNA polymers via phosphodiester bonds, vital for General Biology certification mastery.
Question
Nucleic acids are polymers of nucleotides. Each nucleotide is composed of:
A. a glucose sugar, a nitrogenous base, and a phosphate group.
B. a ribose sugar, a nitrogenous base, and a phosphate group.
C. a ribose sugar, a nitrogenous base, and a ferrous group.
D. a glucose sugar, a nitrogenous base, and a ferrous group.
Answer
B. a ribose sugar, a nitrogenous base, and a phosphate group.
Explanation
Nucleic acids, including DNA and RNA, form long polymers where each nucleotide monomer consists of a five-carbon ribose sugar (deoxyribose in DNA with 2′ hydrogen, ribose in RNA with 2′ hydroxyl), one of five nitrogenous bases (purines adenine/guanine or pyrimidines cytosine/thymine-uracil), and one to three phosphate groups linked via phosphodiester bonds. The sugar’s 1′ carbon bonds covalently to the base’s N1 (pyrimidine) or N9 (purine), while the 5′ sugar carbon connects to phosphate, and the 3′ carbon links to the next nucleotide’s phosphate, creating the polynucleotide backbone that stores genetic information through base sequence. Glucose (six-carbon aldose used in glycogen/cellulose) and ferrous groups (iron-related, irrelevant to nucleotides) do not feature in nucleotide structure, distinguishing nucleic acids from carbohydrates.