MCQ Detailed View

Plants and animals are both living organisms, but their structures and storage materials are different. One key substance that is present in plants but absent in animals is cellulose.

Cellulose is a complex carbohydrate and an important structural polysaccharide. It is the main component of the plant cell wall, giving plants their rigid structure and helping them stand upright. Without cellulose, plants would not be able to maintain their shape, protect their cells, or grow tall. This makes cellulose unique to plants, algae, and some bacteria, but it is completely absent in animals.

Animals, on the other hand, do not have cell walls. Their cells are surrounded only by a flexible cell membrane. Because of this, animals cannot produce cellulose in their bodies. Instead of cellulose, animals rely on bones, cartilage, or exoskeletons (in insects and crustaceans) for structural support.

Interestingly, while animals cannot make cellulose, many herbivores such as cows, goats, and horses can digest plant material containing cellulose. However, they cannot do it directly — they depend on special bacteria in their digestive systems that help break down cellulose into simpler sugars. Humans cannot digest cellulose either, which is why it acts as dietary fiber in our food, helping with digestion and bowel movement.

The other options in the question can be confusing for learners:

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  Starch is found in plants as a storage carbohydrate, but animals also have glycogen (a similar storage molecule).

  
  


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  Protein is found in both plants and animals.

  
  


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  Fat is also present in both plants (as oils) and animals (as lipids).

  
  

Therefore, the correct answer is Cellulose, the unique plant substance absent in animals.