For a transport to be classified as "active" (Low to High), it requires three distinct elements:
Receptor-mediated Endocytosis: A highly specific process where cells take in specific molecules (like cholesterol) only after they bind to receptors on the surface. Exocytosis active transport low to high
Antiport: The molecules move in opposite directions. The sodium-calcium exchanger is a common example, where sodium enters the cell to help pump calcium out. Bulk Transport: Moving Large Quantities For a transport to be classified as "active"
The process of active transport involves several steps: active transport low to high
Pinocytosis: Known as "cell drinking," where the cell takes in fluids and dissolved solutes.
Maintaining the electrochemical gradient across the cell membrane. Secondary Active Transport