Active Transport

What is Active Transport ?

Active Transport is the movement of particles from a place of low concentration to a place of high concentration (AGAINST the concentration gradient)
Requires a protein which is often called a "pump" because it functions to pump molecules across the cell membrane against the concentration gradient.
This process REQUIRES ATP (ENERGY)!
An example of active transport is when iodine in thyroid glands or when Na+ and K+ ions are moved across the cell membrane of nerve cells (Na/K pumps)

Steps:

Sodium (Na+) ions want to go from an area of low concentration to a place of high concentration.
Sodium ions bind to the sodium-potassium pump (protein pump) and wait for an ATP molecule to break apart so enough energy can be generated in order to change the pumps shape. The protein pump will change shape when one of the phosphate groups on the ATP molecule break apart and attach to one end of the protein pump in order to initiate its shape change.
The sodium ions are released on the other side of the membrane where there is a high concentration of sodium ions. The new shape of the protein pump now allows new potassium (K+) ions to bind to it in order to travel to the other side of the cell membrane where there is a high concentration of potassium ions.
When the phosphate group unbinds to the protein pump it causes the protein to revert back to its original shape which further allows the potassium ions to be released onto the other side of the membrane.
This process continues until there is an equal concentration of Na+ and K+ ions on both sides of the cell membrane.

Endocytosis is the movement of LARGE particles to the inside of the cell membrane through the formation of vesicles
This process requires ATP (energy) in order to work.
There are two ways endocytosis works either through the process of Phagocytosis and Pinocytosis

Allows the cell to release particles
This process works as secretory vesicles (vesicles secreted by organelles such as the Golgi apparatus in the cell) fuse with the cell membrane and gradually release its contents and particles.
This process requires ATP
Proteins and hormones are transported through exocytosis

EXOCYTOSIS

ENDOCYTOSIS