Pepsin is secreted in an inactive form as pepsinogen because

  • A. an active enzyme would digest the protein of the cells that make it
  • B. pepsinogen is easier to store in the blood
  • C. pepsin cannot be transported across a membrane
  • D. pepsinogen digests fat before it is converted

Explanation

Pepsin is a protease, and the cells that secrete it are themselves made of protein, so it is released as an inactive precursor and converted to the active enzyme by hydrochloric acid only after it is safely inside the stomach lumen. Trypsin is handled in the same way, being secreted as trypsinogen and activated by enterokinase in the duodenum. This is a general safety principle for digestive proteases.

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