Active transport is the movement of a substance across a cell membrane with the input of energy (ATP). During active transport, proteins move substances against a concentration gradient, from an area of low concentration to an area of high concentration, generally with the help of transfer proteins, thus requiring energy.

Image is of active transport. It shows a hydrogen ion being pumped through a protein pump. The hydrogen is moving against the concentration gradient and therefore requires energy in the form of ATP.

Video segment. Assistance may be required. Watch the following video on the Sodium Potassium Pump which is an example of active transport.

Source: Active Transport, micrbett, YouTube

Types of Active Transport

Sometimes, the cell needs to move large molecules into and out of the cell.  When these molecules are too big to pass through the plasma membrane, the cell utilizes the process of endocytosis and exocytosis. 

  • Endocytosis is the process in which a small patch of plasma membrane encloses particles or tiny volumes of fluid that are at or near the cell surface. The membrane enclosure then sinks into the cytoplasm and pinches off from the membrane, forming a vesicle that moves into the cytoplasm.

  • Exocytosis is the reverse of endocytosis. During exocytosis, the membrane of the vacuole surrounding the material fuses with the plasma membrane, forcing the contents out of the cell.  

Image shows endocytosis and exocytosis.
 Adapted from Endocytosis and Exocytosis.
Source: Running Strong- A Science Library

 

Video segment. Assistance may be required. Watch this video on endocytosis and exocytosis.

Source: Endocytosis and Exocytosis, cecamgmacz, YouTube