Single-celled Paramecium live in pond water (a hypotonic environment relative to the cytosol). They have a structural feature, a contractile vacuole, which enables them to osmoregulate. If sucrose or saline was added to the pond water in different concentrations (in millimolars, mM), under which conditions would you expect the contractile vacuole to be most active?
A) 0.0 mM sucrose
B) 0.05 mM saline
C) 0.08 mM sucrose
D) 1.0 mM saline

Question

Quizplus · Accepted Answer

The contractile vacuole is most active in hypotonic environments to expel excess water. 0.0 mM sucrose represents the most hypotonic condition, leading to increased water influx and thus more activity of the contractile vacuole.

Single-Celled Paramecium Live in Pond Water (A Hypotonic Environment Relative