Lysis in tap water animal cell versus plant cell?

Answer 1

When an animal cell is placed in tap water, it would usually expand to such an extent (filling up with tap water molecules) that lysis occurs (i.e. the bursting/breaking open of the cell). This is due to the differences in water concentration between the inside and outside of the cell (and hence osmotic pressures) - water moves by osmosis across a semi-permeable membrane from an area of higher concentration to an area of lower concentration [in this case the tap water moves across the animal cell membrane into the cell] Because of the lack of membrane support present in an animal cell (i.e. no cell wall providing support), once the water from outside has filled up the animal cell to a certain extent, lysis will occur and the contents of the cell will disperse, no longer held in by a membrane. However, in a plant cell, which has a rigid cell wall made of cellulose as well as a cell membrane, when water moves into the cell by osmosis, lysis will not occur because of the turgor pressure built up against the cell wall. In a hypotonic solution (e.g. tap water), a plant cell is under its best conditions. The cell is turgid - filled with the maximum amount of water, and the cell wall prevents lysis from occurring. (e.g. putting a stick of limp celery in tap water will not result in the contents of the celery breaking apart everywhere, but instead, the water from outside will fill the celery causing it to be crisp - due to osmosis)