active transport
Quick Summary
Active transport is the movement of chemical substances across a cell membrane against their concentration gradient, requiring energy expenditure. This process is crucial for maintaining cellular functions, as cells often need to import nutrients or export waste products even when concentrations are not favorable for spontaneous diffusion.12
There are two main types of active transport:
* Primary active transport directly uses metabolic energy, such as the hydrolysis of ATP, to move substances. A key example is the sodium-potassium pump, which moves sodium ions out of and potassium ions into the cell.2
* Secondary active transport uses the energy derived from the movement of one substance down its concentration gradient to power the movement of another substance against its gradient. This can occur through counter-transport (substances move in opposite directions) or co-transport (substances move in the same direction).34
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