Which sugar is an important component of ATP, FAD, NAD, RNA, and DNA?

The correct choice is ribose, which plays a fundamental role in the structure of various essential biomolecules. Ribose is a five-carbon sugar (pentose) that is a critical component of adenosine triphosphate (ATP), flavin adenine dinucleotide (FAD), and nicotinamide adenine dinucleotide (NAD), all of which are vital for energy transfer and metabolic processes within cells. Additionally, ribose is a building block of ribonucleic acid (RNA), which is crucial for protein synthesis and gene expression.

In contrast, deoxyribose, while also a sugar, is specific to DNA and lacks one oxygen atom compared to ribose, indicating a structural difference. Glucose and galactose are six-carbon sugars (hexoses) primarily involved in energy metabolism but are not components of RNA, DNA, ATP, or the cofactors mentioned. Thus, ribose is specifically important due to its presence in these key biological molecules, while the other sugars have different roles and structures.