To be absorbed by cells, proteins must be changed to:

To be utilized by cells, proteins need to be broken down into their fundamental building blocks, which are amino acids. This process occurs during digestion, where enzymes in the stomach and intestines cleave the peptide bonds between amino acids in proteins. Once proteins are digested into amino acids, they can easily pass through the cell membranes and be absorbed by the cells. Amino acids play critical roles in various biological processes, including the synthesis of new proteins, enzymes, and hormones, as well as serving as precursors for other biomolecules.

The other substances listed—sucrose, fatty acids, and glycerol—are products derived from the digestion of carbohydrates and lipids, not proteins. Sucrose is a disaccharide sugar that must be broken down into glucose and fructose for absorption; fatty acids and glycerol are products of lipid digestion. Thus, the correct answer emphasizes the specific breakdown of proteins into amino acids, which is essential for cellular absorption and function.