Which statement about carbohydrates is true?

Which statement about carbohydrates is true?

• A. Carbohydrates are built from amino acids and are never used for energy.
• B. Carbohydrates are polymers of nucleotides and serve as enzymes.
• C. Carbohydrates are formed from monosaccharides and polysaccharides and glucose is a carbohydrate.
• D. Carbohydrates have monomers called monosaccharides, polymers called polysaccharides, are used for energy, and glucose is a carbohydrate.

Answer: (D)

Carbohydrates are built from simple sugar units called monosaccharides, and when these units link together they form larger polymers called polysaccharides. A central role of carbohydrates is providing energy: cells break down glucose, a common monosaccharide, to generate ATP. Glucose is itself a carbohydrate, and it serves as a primary quick-energy source for many organisms. The option that fits best states that carbohydrates have monomers (monosaccharides), polymers (polysaccharides), are used for energy, and glucose is a carbohydrate. The other statements misrepresent what carbohydrates are or what they do: one says they’re built from amino acids and never used for energy (carbohydrates aren’t built from amino acids and they do provide energy); another says they’re polymers of nucleotides and serve as enzymes (nucleotides form nucleic acids; enzymes are typically proteins or RNA, not carbohydrates); and another is incomplete, mentioning formation from monosaccharides and polysaccharides without noting their energy-use role.

Carbohydrates are built from simple sugar units called monosaccharides, and when these units link together they form larger polymers called polysaccharides. A central role of carbohydrates is providing energy: cells break down glucose, a common monosaccharide, to generate ATP. Glucose is itself a carbohydrate, and it serves as a primary quick-energy source for many organisms.

The option that fits best states that carbohydrates have monomers (monosaccharides), polymers (polysaccharides), are used for energy, and glucose is a carbohydrate. The other statements misrepresent what carbohydrates are or what they do: one says they’re built from amino acids and never used for energy (carbohydrates aren’t built from amino acids and they do provide energy); another says they’re polymers of nucleotides and serve as enzymes (nucleotides form nucleic acids; enzymes are typically proteins or RNA, not carbohydrates); and another is incomplete, mentioning formation from monosaccharides and polysaccharides without noting their energy-use role.