MEMBRANE TRANSPORT INVOLVES THE MOOVEMENT OF SUBSTANCES ACROSS THE CELL MEMBRANE
Transport through the Cell Membrane Occurs through Diffusion or Active Transport
- Diffusion means random movement of molecules either through intermolecular spaces in the cell membrane or in combination with a carrier protein. The energy that causes diffusion is the energy of the normal kinetic motion of matter.
- Active transport means the movement of substances across the membrane in combination with a carrier protein but also against an electrochemical This process requires a source of energy in addition to kinetic energy.
DIFFUSION
Diffusion Is the Continual Movement of Molecules in Liquids or Gases. Diffusion through the cell membrane is divided into the following two subtypes:
- Simple diffusion means that molecules move through a membrane without binding with carrier proteins. Simple diffusion can occur by way of two pathways: (1) through the interstices of the lipid bilayer and (2) through watery channels in transport proteins that span the cell
- Facilitated diffusion requires a carrier The carrier protein aids in the passage of molecules through the membrane, probably by binding chemically with them and shuttling them through the membrane in this form.