Question

which functional group is present in carbohydrates? see figures below.

if you are having trouble seeing the figure then click this link to see the figure in a new window:
carbohydrate functional groups
need a hint? check out this version of the figure that has all of the functional groups circled:
carbohydrate functional groups circled

☐ carboxyl
☐ phosphate
☐ amino
☐ hydroxyl
☐ methyl
☐ sulfhydryl

Explanation:

Carbohydrates (like the monosaccharide shown) contain multiple -OH (hydroxyl) groups. The structures have several \(\ce{-OH}\) functional groups (e.g., in the linear and ring forms, there are multiple hydroxyl groups attached to carbon atoms). Carboxyl (\(\ce{-COOH}\)) has \(\ce{-C=O}\) and \(\ce{-OH}\) on the same carbon (not dominant here), phosphate has \(\ce{-PO4}\), amino has \(\ce{-NH2}\), methyl is \(\ce{-CH3}\), and sulfhydryl is \(\ce{-SH}\) – none of these match the dominant functional group in carbohydrates as seen in the figures.

Answer:

D. Hydroxyl (assuming the option for Hydroxyl is labeled as such; if the option identifier for Hydroxyl is, e.g., the fourth option, then the answer would be the option with "Hydroxyl" text, e.g., if the options are ordered as given: the fourth option: Hydroxyl)