Final answer:
The backbone of a DNA molecule is composed of phosphate molecules and deoxyribose sugars. These alternate to form the DNA structure's sides, with nitrogenous base pairs as the rungs. The correct answer is c) Phosphate molecules and deoxyribose sugars.
Step-by-step explanation:
The backbone of a DNA molecule is composed of two types of molecular components: phosphate molecules and deoxyribose sugars. These components alternate to form the sides of the DNA ladder-like structure, while the rungs of the ladder are composed of nitrogenous base pairs. When considering the structure of nucleic acids, it's important to note that DNA has deoxyribose as its sugar, whereas ribonucleic acid (RNA) has ribose, which includes an additional hydroxyl group.
Each nucleotide in DNA consists of a phosphate group, a deoxyribose sugar, and a nitrogen-containing base. DNA is double-stranded, with the two strands running in opposite directions, known as an antiparallel orientation. This is essential for DNA replication and for many nucleic acid interactions. Nucleotides are connected by phosphodiester linkages, forming the long chain that makes up each strand of the double helix. In this structural arrangement, the phosphate and deoxyribose form the external backbone while the nitrogenous bases face inward, paired with complementary bases across the two strands, connected by hydrogen bonds.
Therefore, the correct answer to the question "The backbone of a DNA molecule is made of which two compounds?" is option c) Phosphate molecules and deoxyribose sugars. This reflects the components of a DNA nucleotide and the fundamental building blocks of a DNA molecule's structure.