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Question Video: Describing the Main Function of the Digestive System Biology

What is the main function of the digestive system?

02:03

Video Transcript

What is the main function of the digestive system? (A) Synthesizing large molecules from smaller ones. (B) Collecting and processing information from external and internal stimuli. (C) Regulating cellular metabolism and respiration. (D) Breaking down large, insoluble molecules into smaller, soluble ones. Or (E) maintaining a constant internal environment.

Whether we choose a healthy green smoothie or not-so-healthy french fries, the food we ingest takes an amazing journey through the digestive system, starting at the mouth and ending at the rectum. The main organs of the digestive system are shown in the diagram and include the esophagus, stomach, and small and large intestines, as well as critical accessory organs, such as the liver and pancreas.

Digestion is a process in which large molecules, or macromolecules, are broken down into smaller molecules. It is essential because unless the large, insoluble nutrients in food are broken into smaller forms, they will not be absorbed into the bloodstream. And we will not be able to use them for cellular respiration, growth, or repair.

The biological macromolecules in food are broken down into their smaller subunits, or monomers, by enzymes that are specific to the type of substrate they break down. For example, proteins are broken into amino acids by a group of enzymes called proteases. Once they are fully broken down, the monomers move out of the digestive system into surrounding capillaries. The blood then carries these smaller nutrients to the body cells, where they can be reassembled into an incredibly diverse range of molecules to be used by the body.

Returning to our answer options, we can see that the correct answer is (D). The main function of the digestive system is breaking down large, insoluble molecules into smaller, soluble ones.

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