Which of the following components of a tossed salad will pass through the human digestive tract and be digested the least?

• A. Sugar (in the dressing)
• B. Oil (in the dressing)
• C. Starch (in the croutons)
• D. Protein (in the bacon bits)
• E. Cellulose (in the lettuce)

Answer: (E)

Verified step by step guidance

1. Identify the components of the salad: sugar, oil, starch, protein, and cellulose.
2. Understand that cellulose is a type of carbohydrate found in plant cell walls, such as those in lettuce.
3. Recognize that humans lack the enzyme cellulase, which is necessary to break down cellulose into glucose units.
4. Compare this with other components: sugars, oils, starches, and proteins, which can be digested by enzymes like amylase, lipase, and protease.
5. Conclude that cellulose will pass through the digestive tract largely undigested, unlike the other components which are broken down and absorbed.