Transportprotein

Transporters are proteins in the broader sense that perform or facilitate transport of certain substances, wherein the target site within the same cell, directly outside the cell or even a different place can be within a multicellular organism. In the narrow sense refers to a protein transport protein, which is located stationary in the cell membrane and the transport through the cell membrane passive facilitated (for example, ion channel ) or actively effected (for example, the ion pump ).

In contrast to processes based on diffusion transfer of the protein- dependent transport shows typical kinetic parameters to those of the enzyme-catalyzed reactions are analogous. To display transport proteins a saturation behavior with increasing substrate concentrations and, where appropriate, the various forms of inhibition.

Transport through the cell membrane

Transmembrane transport proteins (sometimes called permeases ) transport of materials and in the cell, either passively with the concentration gradient, or against the concentration gradient under direct or indirect energy consumption ( active transport ). If one went earlier of mobile carriers in biological membranes ( valinomycin ) model, as we now know that most membrane transport proteins are stationary in the membrane.

In this class of transport proteins include proteins in organelle membranes, since they do not differ fundamentally from those of the cell membrane. Thus, particularly in shuttle systems participating enzymes such as malate dehydrogenase of Malatschleuse are referred to as transport protein.

The subdivision of the membrane transport proteins are corresponding to the subdivision of membrane transport (qv) in:

  • Transporter (carrier ) for the Uniport, catalyzed permeation ( single molecules are transported in one direction).
  • Symport, cotransport (simultaneous transportation of two / three different particles in the same direction )
  • Antiport, counter- transport (simultaneous transportation of two / three different particles in opposite direction)

Transport outside of cells

For the transport of substances in the bloodstream, most of these substances are bound to specific carrier proteins.

Transport proteins in the blood include:

  • Albumin
  • Haemoglobin: binds oxygen and carbon monoxide
  • Haptoglobin: hemoglobin binds
  • High Density Lipoprotein: binds fats
  • Low Density Lipoprotein: binds fats
  • Thyroxine - binding globulin: binds the thyroid hormone thyroxine
  • Transcortin: binds steroid hormones
  • Transferrin binds iron
  • Vitamin D binding protein: binds vitamin D
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