Chemical digestion reduces large complex molecules to simpler compounds by the process of __.
A) mastication
B) catabolism
C) anabolism
D) fermentation
The correct answer is B) catabolism.
Explanation:
Chemical digestion is the process by which large, complex food molecules (such as proteins, carbohydrates, and fats) are broken down into smaller, simpler molecules that the body can absorb and use. This process occurs in the digestive system, specifically in the stomach and small intestine, with the help of enzymes and other digestive substances.
Catabolism refers to the set of metabolic processes that break down large, complex molecules into smaller units, often releasing energy in the process. During chemical digestion, enzymes like amylase, lipase, protease, and others catalyze the breakdown of carbohydrates, lipids, and proteins. For example:
- Carbohydrates are broken down into simple sugars like glucose.
- Proteins are broken down into amino acids.
- Lipids (fats) are broken down into fatty acids and glycerol.
This breakdown is necessary because the body cannot absorb large macromolecules directly into the bloodstream. The smaller molecules produced through catabolism are then transported across the walls of the digestive tract into the bloodstream and lymphatic system, where they can be used for energy production, growth, and repair.
Now, let’s look at the other options:
- A) Mastication: This refers to the mechanical process of chewing, which breaks down food into smaller pieces but does not involve the chemical transformation of molecules.
- C) Anabolism: This is the opposite of catabolism. Anabolism is the process of building up complex molecules from simpler ones, such as when amino acids are assembled into proteins or glucose is stored as glycogen.
- D) Fermentation: This is a biological process that occurs in some organisms, where sugars are converted into energy, typically in the absence of oxygen, but it is not directly related to the process of digestion in humans.
Thus, chemical digestion involves catabolism—the breakdown of complex molecules into simpler compounds.