Question

The complete digestion of starch in human yields 4 kilocalories per gram. What is the energy yield for cellulose in humans?

a) 0 kilocalorie per gram
b) 1 kilocalorie per gram
c) 2 kilocalories per gram
d) 3 kilocalories per gram
e) 4 kilocalories per gram

Answer 1

Humans cannot digest cellulose; therefore, it provides 0 kilocalories per gram of energy. Cellulose serves as dietary fiber, contributing to the digestive process but not to caloric intake.

Step-by-step explanation:

The energy yield for cellulose in humans is technically 0 kilocalories per gram because humans lack the necessary enzyme to digest cellulose. Unlike starch, which is digested into glucose units that each provide 4 kilocalories of energy, cellulose remains undigested as it passes through the human digestive system. Cellulose is considered dietary fiber which aids in digestion but does not contribute significant caloric energy as digestible carbohydrates do.

Thus, while digestion of carbohydrates like starch and sugars yields energy that can be measured in calories, also known as kilocalories, undigestible carbohydrates such as cellulose do not provide energy that the human body can directly extract or quantify in such terms.