Which substance can be converted to glucose when blood glucose levels fall?

The correct choice is proteins because they contain amino acids, some of which can be converted into glucose through a process called gluconeogenesis. This process primarily takes place in the liver and allows the body to maintain blood glucose levels during times of fasting or low carbohydrate intake. When blood glucose levels fall, the body can draw on amino acids derived from the breakdown of proteins to synthesize glucose, ensuring a consistent energy supply for vital functions.

Fats, while they can be converted into energy, do not form glucose directly and are instead broken down into fatty acids and glycerol. Vitamins and minerals play crucial roles in metabolic processes and overall health but do not provide a direct source of glucose when blood sugar levels drop. Therefore, proteins are the primary macronutrient that can be converted to glucose in response to decreased blood glucose levels.