Which of the following is NOT true regarding carbohydrate structure and function?

• A. Monosaccharides can exist in both linear and cyclic forms.
• B. Glycosidic bonds link monosaccharide units in disaccharides and polysaccharides.
• C. All carbohydrates contain only carbon, hydrogen, and oxygen atoms.
• D. Cellulose is a storage polysaccharide in animals.

Answer: (D)

Verified step by step guidance

1. Step 1: Begin by understanding the structure and function of carbohydrates. Carbohydrates are organic molecules composed of carbon (C), hydrogen (H), and oxygen (O) atoms, typically in a ratio of 1:2:1. They serve various roles, including energy storage, structural support, and cell signaling.
2. Step 2: Review the statement 'Monosaccharides can exist in both linear and cyclic forms.' Monosaccharides, such as glucose, can indeed exist in both linear and cyclic forms due to the ability of the carbonyl group to react with a hydroxyl group within the same molecule, forming a ring structure.
3. Step 3: Examine the statement 'Glycosidic bonds link monosaccharide units in disaccharides and polysaccharides.' Glycosidic bonds are covalent bonds formed between the hydroxyl groups of two monosaccharides during a dehydration reaction, linking them into larger carbohydrate structures like disaccharides and polysaccharides.
4. Step 4: Analyze the statement 'All carbohydrates contain only carbon, hydrogen, and oxygen atoms.' This is true for most carbohydrates, as their general formula is (CH2O)n, where n is the number of carbon atoms. However, some modified carbohydrates may contain additional elements, such as nitrogen or sulfur.
5. Step 5: Evaluate the statement 'Cellulose is a storage polysaccharide in animals.' Cellulose is actually a structural polysaccharide found in plants, not animals. Animals store carbohydrates primarily as glycogen, making this statement incorrect.