Final answer:
Pepsinogen is the precursor to pepsin, an enzyme that functions in the stomach, produced by chief cells and activated by HCl.
Step-by-step explanation:
The precursor to an enzyme that functions in the stomach is pepsinogen. Pepsinogen is an inactive enzyme produced by chief cells in the stomach lining, which is converted into its active form, pepsin, in the presence of hydrochloric acid (HCl). This conversion is initiated by the drop in pH when food enters the stomach. Pepsin then plays a crucial role in protein digestion by catalyzing the hydrolysis of peptide linkages within protein molecules, especially those involving aromatic amino acids and certain other amino acids. The presence of pepsin and its precursor pepsinogen are essential for the effective breakdown of proteins into peptides which can then be further digested in the small intestine.
The precursor to an enzyme that functions in the stomach is (a) pepsinogen.
Explanation: Pepsinogen is an inactive enzyme produced by the chief cells in the stomach lining. When food enters the stomach and the pH drops, pepsinogen is converted to its active form, pepsin, which functions to catalyze the hydrolysis of peptide linkages within protein molecules.
For example, if we consider the digestion of a protein, pepsin would break the peptide bonds between the amino acid residues in the protein, resulting in the formation of smaller protein fragments called peptides.