Final answer:
Cellulose and lignin are both found in fruits and vegetables and are indigestible fibers that contribute to dietary fiber. They are not digested because humans lack the necessary enzyme to break them down, making the original statement false.
Step-by-step explanation:
The statement 'Cellulose and lignin are two types of indigestible fiber found in fruits but not in vegetables' is false. Both cellulose and lignin are types of dietary fiber found not only in fruits but also in vegetables. Cellulose is a polysaccharide that is a major component of the cell wall of green plants, including both fruits and vegetables, and contributes to dietary fiber.
Humans cannot digest cellulose because we do not produce the enzyme cellulase which is necessary to break down the β-glycosidic linkages in cellulose. Therefore, it adds bulk to our diet and aids in the movement of food through the digestive tract, providing benefits such as promoting a healthy digestive tract and reducing the risk of certain diseases.
Lignin, another indigestible component, is also present in both fruits and vegetables.