Question

The 5′ end of a nucleic acid molecule refers to the ___________ group on the 5′ carbon of the first nucleotide.

a) hydroxyl
b) carboxyl
c) carbonyl
d) phosphate
e) none of the above

Answer 1

The 5′ end of a nucleic acid molecule refers to the phosphate group on the 5′ carbon of the first nucleotide, which is part of the sugar-phosphate backbone essential for nucleic acid structure.

Step-by-step explanation:

The 5′ end of a nucleic acid molecule refers to the phosphate group on the 5′ carbon of the first nucleotide. Therefore, the correct answer is d) phosphate. The 5′ and 3′ ends of a nucleic acid strand signify the directionality of the strand, with the 5′ end having a terminal phosphate group and the 3′ end usually having a terminal hydroxyl group.

The structure of a nucleic acid includes a backbone made up of sugar and phosphate groups, with the sugar being either ribose in RNA or deoxyribose in DNA. The phosphate group is crucial for the formation of the sugar-phosphate backbone by forming phosphodiester linkages between the 5′ carbon of one nucleotide and the 3′ carbon of the next. This configuration is essential for the polymerization of nucleotides into strands of nucleic acid.