Extracellular enzymes act outside the cell

Steps:

• Define extracellular enzymes as those secreted by cells to function in external environments like digestive tracts.
• Review option A: Amylase in saliva operates in the mouth, outside cells.
• Check options B-D: All are located and function within cellular compartments.
• Confirm A matches the extracellular criterion while others do not.

Why A is correct:

• Salivary amylase is secreted by salivary glands into the oral cavity, exemplifying an extracellular enzyme per the definition of enzymes released to break down substrates outside the cell.

Why the others are wrong:

• B: ATP synthase resides in the inner mitochondrial membrane, an intracellular site.
• C: DNA polymerase functions within the nucleus during replication, intracellularly.
• D: RNA polymerase operates in the nucleus for transcription, intracellularly.

Final answer: A