What passes through the digestive tract as fiber or roughage? Multiple Choice glycogen cellulose glucose maltose starch
The correct answer and explanation is:
Correct Answer: Cellulose
Explanation:
The substance that passes through the digestive tract as fiber or roughage is cellulose. Cellulose is a complex carbohydrate and a type of polysaccharide made up of glucose molecules linked together in a way that the human digestive enzymes cannot break down.
What Is Cellulose?
Cellulose is found in the cell walls of plants and provides structural support. It is the most abundant organic polymer on Earth. When humans eat plant-based foods (like fruits, vegetables, whole grains, and legumes), they also consume cellulose as part of dietary fiber.
Why Can’t Humans Digest Cellulose?
Human digestive systems lack the enzyme cellulase, which is needed to break the β(1→4) glycosidic bonds in cellulose. As a result, cellulose passes through the digestive system largely undigested. However, this is actually beneficial because:
- It adds bulk to stool, which helps prevent constipation.
- It promotes healthy bowel movements by stimulating peristalsis (muscle contractions of the intestines).
- It helps regulate blood sugar and cholesterol by slowing absorption of sugar and fat.
Why Not the Other Options?
- Glycogen is a storage form of glucose in animals and is easily broken down during digestion.
- Glucose is a simple sugar that is absorbed directly into the bloodstream in the small intestine.
- Maltose is a disaccharide (two glucose units) and is broken down into glucose by the enzyme maltase.
- Starch is a digestible plant polysaccharide made of α(1→4) glucose linkages, broken down by enzymes like amylase.
In contrast, cellulose’s unique structure makes it indigestible, classifying it as insoluble fiber. It does not provide calories but plays a crucial role in maintaining digestive health. That’s why it is commonly referred to as roughage.