Cells often need to "pull in" nutrients even when they are already more concentrated inside the cell than in the external environment.
These are just a few examples of molecules that use active transport. The process is essential for maintaining proper cellular function, regulating the concentration of essential molecules, and removing waste products.
Maintained at very low concentrations inside the cytoplasm by ATP-driven pumps to prevent unwanted cell signaling. Hydrogen Ions (H+) what molecules use active transport
Glucose is often used as the classic “passive transport” example via GLUT transporters, but , glucose is reabsorbed via secondary active transport:
This paper focuses on the ABC (ATP-Binding Cassette) superfamily, which is one of the largest families of active transporters. Cells often need to "pull in" nutrients even
This maintains the cell’s resting potential and drives other secondary transport processes.
Active transport is a cellular process that moves molecules across a membrane against their concentration gradient (from an area of low concentration to high concentration). Unlike passive transport, this "uphill" movement requires energy, usually in the form of Adenosine Triphosphate (ATP). Maintained at very low concentrations inside the cytoplasm
Start with the Stein paper (or a modern review of ion pumps) if you are interested in basic biology. Search for the International Transporter Consortium paper if you are interested in how drugs or metabolic byproducts are transported.
Cells keep cytosolic calcium extremely low (around 100 nM) compared to outside or in storage organelles. Calcium pumps (Ca²⁺ ATPases) actively move Ca²⁺:
Like glucose, amino acids are often taken up by secondary active transport, co-transported with sodium ions. This happens in the intestine (after protein digestion) and in kidney tubules (to prevent loss in urine).