Transport via Protein Molecules

Transport proteins are also called as carrier proteins or carrier molecules which serve in vital function of body cells that carry specific materials, molecules or ions from one part of the body to another through the circulation or through intracellular compartments or in extracellular fluids. Transport proteins are often globular proteins wherein, these molecules play very important roles that initiate the body regulation of the amount of specific biochemical processes. Most transport proteins facilitates in the movement of specific molecules, chemicals or ions to pass through the cell membrane or plasma membrane.

Each transport protein is very specific that are designed to recognize only one specific substance or one group of very similar substances. The substrate or the molecule, chemical, ion or substance to be transported must first bind at a binding site of the carrier or transport protein molecules which it has a certain binding affinity. After the substrate has associate to the transport protein molecule, it will take in and retain the substrate within its molecular structure and cause an internal shift for the substrate to face the other side of the carrier membrane. The substrate will be discharged at the appropriate site and all steps are reversible.



Since a large number of materials in the body do not dissolve in water, transport protein molecules are generally firmly packed with polar region on the outside to intensify their solubility in water and mostly have non-polar region attached to the inside of the protein to keep water from penetrating and unfolding them.Some of the transport proteins channel a variety of body substances and some are transporters of small hydrophobic molecules which are water-soluble transport proteins that may or may not get across with biological membranes.

Substrate transportation ca be an Active transport or Passive transport:



Active transport involves movement of molecules or ions with the use of certain chemical energy (such as ATP) against the energy of the colliding molecules going through the plasma or cell surface.

Passive transport involves movement of molecules or ions with the flow of the substance molecules without energy required.

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References:

Clinical Chemistry A Fundamental Textbook Donald F. Calbreath
http://en.wikipedia.org/wiki/Transport_protein
http://dl.clackamas.edu/ch106-08/transpor.htm
http://en.wikipedia.org/wiki/Carrier_protein
http://www.college-cram.com/study/biology/presentations/371