Active Transport
After looking at the first 3 methods of cellular transport, you may wonder "if we can only move molecules in accordance with the concentration gradient, won't everything become evenly spread after a while?" The answer to this question is no, because there are mechanisms that can move molecules against the concentration gradient.
As its name implies, active transport is an active form of transport that requires energy in the form of ATP. Just like facilitated transport, active transport uses protein carriers to move molecules. However, the advantage of active transport over the passive forms of transport is that it can move molecules against the concentration gradient. This is important because it allows the cell to freely increase or decrease the concentration of a certain substance inside it. Cells that use a lot of active transport tend to have more mitochondria to supply the necessary ATP for it.
For example, the sodium-potassium pump in neurons moves sodium ions out of the cell and potassium ions into the cell against the concentration gradient.
As its name implies, active transport is an active form of transport that requires energy in the form of ATP. Just like facilitated transport, active transport uses protein carriers to move molecules. However, the advantage of active transport over the passive forms of transport is that it can move molecules against the concentration gradient. This is important because it allows the cell to freely increase or decrease the concentration of a certain substance inside it. Cells that use a lot of active transport tend to have more mitochondria to supply the necessary ATP for it.
For example, the sodium-potassium pump in neurons moves sodium ions out of the cell and potassium ions into the cell against the concentration gradient.