flux
Quick Summary
The term "flux" has multiple meanings, including a continuous flow, a state of change, or a substance used to promote fusion. In cell physiology, flux refers to the rate of transfer of fluid, particles, or energy across a given surface, particularly the cell membrane.1
The cell membrane acts as a barrier and a gate, controlling what enters and leaves the cell. While lipid-soluble molecules can pass through, larger, water-soluble molecules and ions require specific transport systems. These systems include channels, facilitators, and pumps.234
Transport mechanisms:
* Passive transport: Solutes move down their concentration gradient without external energy input, utilizing diffusion or facilitated diffusion.23
* Active transport: Requires energy to move solutes against their concentration gradient. This can be primary, directly using metabolic energy, or secondary, where the movement of one solute down its gradient powers the movement of another against its gradient.2
Secondary active transport includes counter-transport, where two substances move in opposite directions across the membrane. This is crucial for maintaining cellular functions, such as regulating ion concentrations.2
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nervous systemLocalized potentialBy permitting a flux of Na+ into the cell, the opening of ion channels slightly depolarizes the membrane. The extent to which the membrane is depolarized depends upon the extent to which the sodium channels are activated, and this in turn depends upon the strength and duration of…
Read MoreBy permitting a flux of Na+ into the cell, the opening of ion channels slightly depolarizes the membrane. The extent to which the membrane is depolarized depends upon the extent to which the sodium channels are activated, and this in turn depends upon the strength and duration of…
Read More- nervous systemPassive transport: membrane channels
…ions across the membrane—specifically, a flux of Na+ into the cell. Given the relative impermeability of the plasma membrane to Na+, this influx itself implies a sudden change in permeability. Beginning in the 19th century, researchers puzzled over the mechanism by which this change could occur. The idea arose that…
Read More…ions across the membrane—specifically, a flux of Na+ into the cell. Given the relative impermeability of the plasma membrane to Na+, this influx itself implies a sudden change in permeability. Beginning in the 19th century, researchers puzzled over the mechanism by which this change could occur. The idea arose that…
Read More