Both pmf and ATP are made by central metabolism and we will cover their formation by the cell later in the semester. Active transport proteins may be highly specific and carry only one molecule or may be more general and carry one class of molecules. The movie of Active Transport shows several different types of transport molecules. An example of a general transport protein is the branch chain amino acid transporter of Pseudomonas aeruginosa , which transports leucine, valine, and isoleucine. The membrane is site for many reactions that lead to the generation of energy.
Many cells use respiratory processes to obtain their energy.
During respiration, organic or inorganic compounds that contain high energy electrons are broken down, releasing those electrons to do work. These electrons find their way to the membrane where they are passed down a series of electron acceptors. During this operation, protons are transported outside the cell. Figure 2 - Generating the proton motive force in a membrane. This proton gradient energizes the membrane, much like a battery is charged.