Which of the following best describes the difference between a simple carbohydrate and a complex carbohydrate?

• A. Simple carbohydrates consist of one or two sugar units (monosaccharides or disaccharides), while complex carbohydrates are composed of many sugar units (polysaccharides).
• B. Complex carbohydrates are made only of glucose, while simple carbohydrates contain a variety of monosaccharides.
• C. Simple carbohydrates provide more energy per gram than complex carbohydrates.
• D. Simple carbohydrates are always insoluble in water, whereas complex carbohydrates are always soluble.

Answer: (A)

Verified step by step guidance

1. Step 1: Begin by understanding the definitions of simple and complex carbohydrates. Simple carbohydrates consist of one or two sugar units, such as monosaccharides (e.g., glucose, fructose) or disaccharides (e.g., sucrose, lactose). Complex carbohydrates, on the other hand, are composed of many sugar units linked together, forming polysaccharides (e.g., starch, glycogen).
2. Step 2: Analyze the first statement: 'Simple carbohydrates consist of one or two sugar units (monosaccharides or disaccharides), while complex carbohydrates are composed of many sugar units (polysaccharides).' This aligns with the definitions provided in Step 1 and is scientifically accurate.
3. Step 3: Evaluate the second statement: 'Complex carbohydrates are made only of glucose, while simple carbohydrates contain a variety of monosaccharides.' This is incorrect because complex carbohydrates can be composed of glucose or other monosaccharides, depending on the polysaccharide structure.
4. Step 4: Assess the third statement: 'Simple carbohydrates provide more energy per gram than complex carbohydrates.' This is incorrect because both simple and complex carbohydrates provide approximately the same energy per gram (4 kcal/g). The difference lies in their digestion and absorption rates, not energy content.
5. Step 5: Examine the fourth statement: 'Simple carbohydrates are always insoluble in water, whereas complex carbohydrates are always soluble.' This is incorrect because simple carbohydrates are generally soluble in water, while the solubility of complex carbohydrates depends on their structure (e.g., starch is insoluble, but glycogen is soluble).