Which statement best describes the carbohydrate source during fasting?

Which statement best describes the carbohydrate source during fasting?

• A. The host's dietary carbohydrates increase
• B. Carbohydrates drop to zero
• C. Bacteria rely on host-derived glycans from saliva
• D. Host cells synthesize more glycans

Answer: (C)

During fasting, there is no influx of dietary carbohydrates, so oral bacteria rely on carbohydrate sources already present in the host environment. Saliva contains glycoproteins and mucins with attached glycans. Bacteria in the biofilm use their glycosidases to cleave these host-derived glycans, releasing sugars they can take up and metabolize for energy. This makes host-derived glycans from saliva the primary carbohydrate source when feeding is not occurring. The other ideas don’t fit because dietary carbs aren’t increasing during fasting, carbohydrates aren’t completely absent (host glycans persist), and there isn’t a need for host cells to suddenly synthesize more glycans to feed the microbes.

During fasting, there is no influx of dietary carbohydrates, so oral bacteria rely on carbohydrate sources already present in the host environment. Saliva contains glycoproteins and mucins with attached glycans. Bacteria in the biofilm use their glycosidases to cleave these host-derived glycans, releasing sugars they can take up and metabolize for energy. This makes host-derived glycans from saliva the primary carbohydrate source when feeding is not occurring. The other ideas don’t fit because dietary carbs aren’t increasing during fasting, carbohydrates aren’t completely absent (host glycans persist), and there isn’t a need for host cells to suddenly synthesize more glycans to feed the microbes.