Transport of Electrolytes across Cell MembranesĮlectrolytes, such as sodium chloride, ionize in water, meaning that they dissociate into their component ions. The blood maintains an isotonic environment so that cells neither shrink nor swell. In a hypotonic environment, cells tend to swell due to intake of water. Cells placed in a hypertonic environment tend to shrink due to loss of water. Isotonic cells have an equal concentration of solutes inside and outside the cell this equalizes the osmotic pressure on either side of the cell membrane which is a semi-permeable membrane. A cell placed in a solution with higher salt concentration, on the other hand, tends to make the membrane shrivel up due to loss of water into the hypertonic or “high salt” environment. As seen in Figure 22.2, a cell placed in water tends to swell due to gain of water from the hypotonic or “low salt” environment. Solutions on two sides of a semi-permeable membrane tend to equalize in solute concentration by movement of solutes and/or water across the membrane. Semi-permeable membranes are permeable (or permissive) to certain types of solutes and water. The membranes of the body (such as the pleural, serous, and cell membranes) are semi-permeable membranes. The body’s fluids include blood plasma, the cytosol within cells, and interstitial fluid, the fluid that exists in the spaces between cells and tissues of the body. Both electrolytes and non-electrolytes contribute to the osmotic balance. A non-electrolyte, in contrast, doesn’t dissociate into ions during water dissolution. An electrolyte is a solute that dissociates into ions when dissolved in water. Osmoregulation is the process of maintenance of salt and water balance ( osmotic balance ) across membranes within the body’s fluids, which are composed of water, plus electrolytes and non-electrolytes. Osmosis is the diffusion of water across a membrane in response to osmotic pressure caused by an imbalance of molecules on either side of the membrane. Describe osmoregulators or osmoconformers and how these tools allow animals to adapt to different environments.Explain osmolarity and the way in which it is measured.Explain why osmoregulation and osmotic balance are important body functions.Define osmosis and explain its role within molecules.
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