Final answer:
A constitutively open ATPase increases proton pumping in the cell.
Step-by-step explanation:
A constitutively open ATPase has the effect of increasing proton pumping in the cell. ATPases are enzymes that use ATP to transport ions across cell membranes. In this case, the ATPase is constitutively open, meaning it is continuously active and pumping protons across the membrane. This increased proton pumping can have various effects on cellular processes that rely on proton gradients, such as ATP synthesis.