The electrolyte solution inside cells has a different composition of solutes than the extracellular electrolyte solution. Inside the cells, potassium, magnesium, and phosphate are in the highest concentrations. Outside the cells, sodium and chloride are in the highest concentrations.
OSMOTIC PRESSURE
Water flows across cell membranes and capillary walls toward the higher concentration of solutes in a process called osmosis. Osmotic pressure tends to equalize concentrations. Osmosis creates a force that is called osmotic pressure and may be offset by hydraulic pressure in a delicate balance. Blood vessels have a higher
hydraulic pressure than interstitial fluid. This extra pressure in blood vessels tends to move water out of the blood vessels and into the interstitial fluid.
This movement of water out of blood vessels is offset by osmotic pressure. There is normally a higher concentration of solutes inside blood vessels. Thus, osmotic pressure tends to move interstitial water into the blood to equalize concentrations.
TRANSPORT OF IONS ACROSS CELL MEMBRANES
Transport proteins embedded in the cell membrane regulate the flow of positive ions across the cell membrane. Negative ions follow the positive ions to maintain a neutral electrolyte balance. Remember that electrolyte solutions must be electrically neutral. Also, water flows across cell membranes toward the more concentrated solution because of osmosis.
One of the best understood transport proteins is the sodium-potassium pump. Proteins embedded in the cell wall actively pump sodium out of the cell while bringing potassium into the cell, as shown in Figure 7-7. First, potassium binds to the protein on the outside of the cell membrane. The protein then flips over, delivering the potassium into the intracellular fluid. Once inside the cell, the now-available
Figure 7-7 Cell membrane transport of sodium and potassium.
protein binds to sodium. Next, the protein flips over again to transport the sodium out of the cell. This kind of active transport requires energy in the form of adenosine triphosphate (ATP).
OSMOTIC PRESSURE
Water flows across cell membranes and capillary walls toward the higher concentration of solutes in a process called osmosis. Osmotic pressure tends to equalize concentrations. Osmosis creates a force that is called osmotic pressure and may be offset by hydraulic pressure in a delicate balance. Blood vessels have a higher
hydraulic pressure than interstitial fluid. This extra pressure in blood vessels tends to move water out of the blood vessels and into the interstitial fluid.
This movement of water out of blood vessels is offset by osmotic pressure. There is normally a higher concentration of solutes inside blood vessels. Thus, osmotic pressure tends to move interstitial water into the blood to equalize concentrations.
TRANSPORT OF IONS ACROSS CELL MEMBRANES
Transport proteins embedded in the cell membrane regulate the flow of positive ions across the cell membrane. Negative ions follow the positive ions to maintain a neutral electrolyte balance. Remember that electrolyte solutions must be electrically neutral. Also, water flows across cell membranes toward the more concentrated solution because of osmosis.
One of the best understood transport proteins is the sodium-potassium pump. Proteins embedded in the cell wall actively pump sodium out of the cell while bringing potassium into the cell, as shown in Figure 7-7. First, potassium binds to the protein on the outside of the cell membrane. The protein then flips over, delivering the potassium into the intracellular fluid. Once inside the cell, the now-available
Figure 7-7 Cell membrane transport of sodium and potassium.
protein binds to sodium. Next, the protein flips over again to transport the sodium out of the cell. This kind of active transport requires energy in the form of adenosine triphosphate (ATP).
More about Macro Minerals:
0 comments