Massachusetts Comprehensive Assessment System (MCAS) Biology Practice Test

During what stage do the simplest forms of molecules become absorbed into the circulatory system?

1. Elimination stage

2. Chemical breakdown stage

3. Absorption stage

4. Mechanical breakdown stage

The correct answer is: Absorption stage

The absorption stage is where the simplest forms of molecules, such as amino acids, fatty acids, and simple sugars, are taken into the circulatory system after digestion. During this stage, the nutrients that have already been broken down into their most basic components in the digestive tract are transported across the intestinal walls into the bloodstream. This process is crucial as it allows the nutrients to be delivered to cells throughout the body where they are utilized for energy, growth, and repair. In contrast, the other stages mentioned focus on different aspects of the digestive process. The elimination stage is when waste products are expelled from the body after digestion. The chemical breakdown stage involves the enzymatic processes that convert complex food molecules into simpler forms, while the mechanical breakdown stage pertains to the physical aspects of digestion, such as chewing and the churning of food in the stomach. These stages precede absorption and are essential but serve distinct functions in the overall digestive process.