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Date of Award


Document Type

Restricted Thesis: Campus only access

Degree Name

Bachelor of Science




The plasma membrane delimits the cell, physically separating the cytoplasm from the surrounding cellular environment. This implies that all substances either entering or exiting the cell must pass through the plasma membrane. The transport of substances across the plasma membrane can be either active or passive. A transport is defined thermodynamically as active if it is observed under conditions where all physical driving forces, such as electrochemical potential, pressure, temperature, and in addition, water flow, across the membrane are zero. The active transport of a solute can be coupled either directly to the cell metabolism via ATP or other energy-rich substrates, resulting in primary active transport, or can be coupled to the flux of another substance whose transport in this case is directly dependent on the cellular metabolism. This cotransport can be either a symport when both substances move in the same direction or an antiport if the directions are opposite. The term passive is used for all other transports that do not fulfill the foregoing requirements. (Kinne, 1976; Wilson, 1979).