AP Biologymediummcq1 pt
Paramecium lives in pond water whose solute concentration is far below that of its cytoplasm, so water continually streams in by osmosis. Which structure and activity keep the organism from swelling?
A.A cellulose cell wall blocks water from ever crossing the plasma membrane.
B.The cell pumps solutes out until its interior matches the pond, permanently erasing the gradient.
C.A contractile vacuole collects incoming water and rhythmically expels it back out through a pore.
D.Aquaporins are stripped from the membrane, switching osmosis off in fresh water.