Plasmolysis

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If a plant cell is placed in a hypertonic solution, the plant cell loses water and hence turgor pressure, making the plant cell flaccid. Plants with cells in this condition wilt. Further water loss causes plasmolysis: pressure decreases to the point where the protoplasm of the cell peels away from the cell wall, leaving gaps between the cell wall and the membrane. Eventually cytorrhysis – the complete collapse of the cell wall – can occur. There are some mechanisms in plants to prevent excess water loss in the same way as excess water gain, but plasmolysis can be reversed if the cell is placed in a weaker solution (hypotonic solution). Stomata help keep water in the plant so it does not dry out. Wax also keeps water in the plant. The equivalent process in animal cells is called crenation. The liquid content of the cell leaks out due to diffusion. The cell collapse and cell membrane pulls away from the cell wall(in plants). Most animal cells consist of only a phospholipid bilayer and not a cell wall, therefore shrinking up under such conditions. Plasmolysis only occurs in extreme conditions and rarely happens in nature. It is induced in the laboratory by immersing cells in strong saline or sugar solutions to cause exosmosis, often using Elodea plants or onion epidermal cells, which have coloured cell sap so that the process is clearly visible. Plasmolysis can be of two types. It can be either concave plasmolysis or convex plasmolysis. Convex plasmolysis is always irreversible while concave plasmolysis is usually reversible.[citation needed]

hagocytosis phagocytosis

Once a white cell has left the blood vessel and migrated to the enemy, the next job is to EAT the microbe. This human macrophage, like its cousin the neutrophil, is a professional "phagocyte" or eating cell (phago = "eating", cyte = "cell"). The macrophage is using its internal cytoskeleton to envelop cells of the fungus Candida albicans. View this sequence in a 510K timelapse movie. But eating the organisms is not enough. To insure that the organisms not grow and divide within the macrophage, the white cell must kill the organisms by some means such as theOXIDATIVE BURST.

Endocytosis is required for a vast number of functions that are essential for the well being of cell. It intimately regulates many processes, including nutrient uptake, cell adhesion and migration, receptor signaling,[1] pathogen entry,[2] neurotransmission, receptor downregulation, antigen presentation, cell polarity, mitosis, growth and differentiation, and drug delivery.[3][4] [edit]

1.hypotonic - (of living tissue) lacking normal tone or tension hypertonic - (of living tissue) in a state of abnormally high tension; "hypertonic muscle tissue" 2.hypotonic - (of a solution) having a lower osmotic pressure than a comparison solution hypertonic - (of a solution) having a higher osmotic pressure than a comparison solution isosmotic, isotonic - (used of solutions) having the same or equal osmotic pressure

isotonic

An isotonic solution contains an equal concentration of impermeable solutes as the solution on the other side of the membrane.[1] If a cell is placed in an isotonic solution, there will be no net movement of water in or out of the cell because the concentration of impermeable solutes in the cell equals that of the external environment. Isotonic saline solution for medical applications has a sodium chloride concentration of 9g per litre of water or 0.9%(w/v). [edit]