r instance, small animal cells such as protozoa, living in fresh water habitats are surrounded by a hypotonic solution and constantly need to expel water using contractile vacuoles to prevent swelling and lysis. On the other hand, cells in marine environments are surrounded by a hypertonic solution, and must actively pump ions into their cells to reduce their water potential and reduce water loss to the surrounding solution by osmosis. Young non-woody plants rely on cell turgor for their support, and without enough water, they will wilt. Plants take up water through their root hair cells by osmosis, and must actively pump ions into their cells to keep them hypertonic compared to the soil. This is particularly difficult if the plants are rooted in salt water.
If a freshwater, unicellular organism was suddenly released into saltwater, it would be more hypotonic than its surrounding solution, and so water would be drawn out of the cell into the more hypertonic solution of its surroundings and the cell would shrink (crenate) (See Figure 1). If a marine organism was placed in freshwater, it would take in water because its contents are hypertonic compared to the freshwater solution, and the cell would swell and most likely lysis would occur (See Figure 1).
"The Cell Membrane." 2005. 22 Apr. 2005.
When large substances need to be transported in or out of cells, changes in the membrane shape and the fusion of the plasma membrane with vesicles containing the substances is necessary to successfully move these substances out of the cell, or the membrane may need to invaginate and fuse to form a vesicle containing the large substance to take it into the cell (Membrane). Movement of Large Molecules Across Cell Menmranes Exocytosis is the process by which materials can be exported out of cells. Vesicle containing the materials, such as secretory granules, or insulin ...