Answer:
cellulose
Step-by-step explanation:
Cellulose is a structural component of plant cell walls and is a type of fiber. While it is a complex carbohydrate made up of repeating glucose units linked together, humans lack the enzymes necessary to break down the cellulose's beta-linkages effectively. As a result, it passes through the digestive system largely undigested and provides bulk to the stool, aiding in digestion and regular bowel movements. It's not a significant source of energy because it's not metabolized in the same way as other carbohydrate.