Osmosis and Osmotic Pressure

Topics: Osmosis, Osmotic pressure, Membrane biology Pages: 3 (540 words) Published: February 24, 2013
icJohn Melvin Mateo
BS AT - 1A NSCI 121

Assignment no.1 (Finals)

1.)What is Osmosis?

Osmosis is the diffusion of the movement of water from a region of higher concentration to a region of lower concentration through a cell membrane or other semi-permeable membrane until an equilibrium is reached. It is a special case of diffusion (passive transport).  Basic Explanation :

Osmosis can occur when there is a partially permeable membrane, such as a cell membrane. When a cell is submerged in water, the water molecules pass through the cell membrane from an area of low solute concentration to high solute concentration (e.g. if the cell is submerged in saltwater, water molecules move out; if it is submerged in freshwater, however, water molecules move in); this is called osmosis. The cell membrane is selectively permeable, so only necessary materials are let into the cell and wastes are left out.[8] The word 'osmosis' is particular to the diffusion of water molecules into the cell.

2.) What is Osmotic Pressure?

Osmotic pressure is the hydrostatic pressure produced by a solution in a space divided by a semipermeable membrane due to a differential in the concentrations of solute.

Osmotic potential is the opposite of water potential with the former meaning the degree to which a solvent (usually water) would want to stay in a liquid.

When a biological cell is in a hypotonic environment (the cell interior contains a lower concentration of water and a higher concentration of other molecules than its exterior), water flows across the cell membrane into the cell, causing it to expand due toosmotic pressure. In plant cells, the cell wall restricts the expansion, resulting in pressure on the cell wall from within called turgor pressure. The osmotic pressure π of a dilute solution can be calculated using the formula

π = iMRT, 

i – is the van 't Hoff factor 
M - is the molarity 
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