Carbohydrates

Step 1: Understand enzyme availability in the animal gut
The animal digestive system is well-equipped with enzymes such as:
Amylase for digesting starch,
Proteases for digesting proteins,
Glycosidase for breaking down glycogen.

Step 2: Analyze cellulose digestion
Cellulose is a polysaccharide made up of β-1,4-linked glucose units.
Animals lack the enzyme cellulase, which is required to hydrolyze these β-1,4 glycosidic bonds.

Step 3: Conclusion
Because animals (especially non-ruminants) do not produce cellulase, they cannot digest cellulose on their own.
In herbivores like cows or termites, microbial symbionts assist in cellulose digestion.

Step 1: Evaluate Statement 1

Statement 1: Glucose is stored in animals as glycogen.
This statement is correct. In animals, glucose is stored in the form of glycogen in the liver and muscles.

Step 2: Evaluate Statement 2

Statement 2: Glucose is stored in plants as starch.
This statement is correct. Plants store glucose in the form of starch, which is made up of amylose and amylopectin.

Step 3: Evaluate Statement 3

Statement 3: Cellulose is a polymer of only glucose.
This statement is correct. Cellulose is indeed a polymer made up of glucose molecules linked by beta-1,4-glycosidic bonds, which forms the structure of plant cell walls.

Step 4: Evaluate Statement 4

Statement 4: Hemicellulose is a polymer of only glucose.
This statement is NOT correct. Hemicellulose is a heterogeneous polysaccharide that contains various sugars, including glucose, but also other sugars like xylose, arabinose, and mannose. It is not made up of glucose alone.

Therefore, the incorrect statement is statement (4).

Step 1: Define epimers.
Epimers are isomers of monosaccharides that differ in configuration at only one specific chiral carbon atom, other than the anomeric carbon. Step 2: Analyze the options.
D-Mannose and D-Glucose differ at C-2 — they are C-2 epimers.
D-Gulose and D-Glucose differ at more than one chiral center.
D-Arabinose and L-Arabinose are enantiomers, not epimers.
D-Glucose and D-Fructose are structural isomers (aldose vs ketose), not epimers.
Conclusion:
Only D-Mannose and D-Glucose qualify as epimers, differing only at the second carbon.