An investigator treats a freshwater protozoan, Amoeba proteus, with dinitrophenol (DNP), a metabolic poison that completely inhibits ATP synthesis. This stops the active transport of water out of the cell via its contractile vacuole. The amoeba is then placed into a sample of pond water, which has a higher water potential than the amoeba's cytoplasm.
What will happen to the amoeba?
Water will enter the cell by osmosis, causing it to swell and eventually burst.
Water will enter the cell by osmosis until the cell becomes turgid and cell wall pressure prevents further net influx.
Water will leave the cell by osmosis, causing it to shrivel (crenate) because ATP is required to maintain internal water potential.
There will be no net movement of water because water transport across the membrane is entirely dependent on active transport mechanisms.
194 exam-style questions on OCR GCSE Biology 2.1 Supplying the cell, covering 2.1.1 Transport across cell membranes, 2.1.2 Mitosis and the cell cycle, 2.1.3 Importance of cell differentiation, and 2.1.4 Stem cells. Each one has a worked solution and a mark scheme showing where the marks go.