Living Environment Regents Practice Test

Which process must occur before the proteins in food can be utilized by body cells?

1. Metabolism

2. Digestion

3. Excretion

4. Respiration

The correct answer is: Digestion

Before the proteins in food can be utilized by body cells, digestion must occur. This process involves breaking down complex food substances into simpler forms that the body can absorb and use. In the case of proteins, digestion begins in the stomach where acids and enzymes break down the protein molecules into smaller peptides and amino acids. These smaller units are then transferred into the small intestine, where they are further digested and absorbed into the bloodstream. Once in the bloodstream, the amino acids can be taken up by cells throughout the body to synthesize new proteins that are essential for various functions, including muscle repair, enzyme production, and immune responses. If digestion does not occur, the proteins remain too large to be absorbed and used, which means that the body cannot access the essential nutrients they provide. Metabolism refers to the sum of all chemical reactions within the body, including both the breaking down of nutrients for energy and the building up of cellular structures, but it cannot happen effectively without the prior digestion of food. Excretion is the process of removing waste products from the body and is not directly related to the initial utilization of proteins. Respiration, on the other hand, pertains to the process of converting glucose and oxygen into energy, which does not specifically address the fate of