Questions: 67. The most likely place where an exoenzyme participates in a chemical reaction is a. mitochondria. b. within the cell membrane. c. lysosomes. d. cytoplasm. e. outside of the cell.

The answer is the last one (e): outside of the cell.

Explanation for each option: a. Mitochondria: Exoenzymes are not typically involved in reactions within mitochondria. Mitochondria are primarily involved in energy production and house enzymes for the citric acid cycle and oxidative phosphorylation, but these are not exoenzymes.

b. Within the cell membrane: While some enzymes are associated with the cell membrane, exoenzymes are specifically those that function outside the cell. Enzymes within the cell membrane are often involved in signaling or transport, not the extracellular activities typical of exoenzymes.

c. Lysosomes: Lysosomes contain enzymes that break down waste materials and cellular debris, but these are not exoenzymes. The enzymes in lysosomes function within the cell to digest intracellular components.

d. Cytoplasm: The cytoplasm contains many enzymes that facilitate intracellular metabolic reactions, but exoenzymes are not among them. Exoenzymes are secreted out of the cell to perform their functions.

e. Outside of the cell: Exoenzymes are enzymes that are secreted by a cell and function outside of that cell. They are involved in breaking down large molecules in the extracellular environment, which can then be absorbed by the cell.

Summary: Exoenzymes are enzymes that are secreted by cells to function outside the cell, making the most likely place for their participation in a chemical reaction outside of the cell.