Which of the following molecules DOES NOT contain at least one carbohydrate? a. nucleotide b. starch c. glycogen d. cholesterol e. a disaccharide
The correct answer and explanation is:
The correct answer is d. cholesterol.
Cholesterol is a type of lipid, not a carbohydrate. It is a sterol, which is a category of lipids with a characteristic structure that includes four hydrocarbon rings. Cholesterol plays an important role in maintaining membrane structure and serving as a precursor for the synthesis of various hormones, but it does not contain carbohydrate units.
Here’s a breakdown of the other options:
- a. nucleotide: Nucleotides are the building blocks of nucleic acids (DNA and RNA). A nucleotide consists of a nitrogenous base, a phosphate group, and a sugar (either ribose or deoxyribose, both of which are carbohydrates). Therefore, nucleotides contain a carbohydrate (the sugar).
- b. starch: Starch is a polysaccharide composed of glucose units linked together. It is a complex carbohydrate used by plants to store energy. Thus, starch is made entirely of carbohydrates.
- c. glycogen: Glycogen is another polysaccharide, but it is the primary form of carbohydrate storage in animals, primarily in the liver and muscles. It is composed of glucose monomers linked together and therefore contains carbohydrates.
- e. a disaccharide: A disaccharide is a sugar composed of two monosaccharides joined together. Examples include sucrose (glucose + fructose) and lactose (glucose + galactose). Disaccharides are carbohydrates.
In summary, cholesterol is the only molecule on the list that does not contain a carbohydrate, as it is classified as a lipid, while the others are either carbohydrates themselves or contain carbohydrate components.