spin around this garden of hope ;
Monday, January 29, 2007 @ 8:22 PM
If the animal cell is to have a cell wall, they will provide rigidity to the cell for structural and mechanical support, maintaining cell shape, the direction of cell growth, and ultimately the architecture of the plant. The cell wall also prevents expansion when water enters the cell. As the young cell forms, the cell wall is initially rather thin and consists of a middle lamella (a sort of pectin glue that holds adjacent cells together) and a primary cell wall. The primary cell wall is flexible enough to allow the cell to grow and mature. Once mature the cell stops growing and the cell wall is strengthened, either by the deposition of secondary substances such as lignin or by the development of a secondary cell wall. This secondary wall often consists of a number of layers and affords great mechanical strength. It is this secondary wall that gives wood its useful properties. So, everyone will be as hard as wood and movement will not really be easy.
The term turgor is used to describe this pressure that is induced by excess water inside the plant cell. Cell walls protect against pathogens in the environment and can store carbohydrates for the cell. Hence, maybe the animal cell can also make by itself in the future The cell wall is constructed primarily from a carbohydrate polymer called cellulose.
Animal cells that have a cell wall will not break open oftenly in solutions whose salt concentrations are either too low (hypotonic) or too high (hypertonic). If the ionic strength of the solution is much smaller than the cell, osmotic pressure forces water into the cell to bring the system into balance, which causes the cell to burst. If the ionic strength of the solution is too high, osmotic pressure forces water out of the cell, and the cell breaks open as it shrinks. The cell wall provides the mechanical strength that can also help protect animal cells that live in fresh-water ponds (too little salt) or seawater (too much salt) from osmotic shock. The cell wall also provides the mechanical strength that allows cells to support the weight of other cells.