∞ generated and posted on 2016.12.16 ∞
Amino acid-based polymeric substance found within lipid bilayers that facilitates the movement of substances across those membranes.
| Transport proteins are responsible for facilitating the movement of substances across lipid bilayers – that is, membranes – and particularly substances that cannot cross lipid bilayers on their own. |
These proteins are responsible for the movement especially of polar molecules. They are absolutely essential for proper cell functioning since otherwise a cell is too limited in what substances it is able to bring in or move out.
Figure legend: Sketch of a transport protein (dumbbell-shape in the center). The stars represent substances that are transferred from one side of the membrane to the other. Because the protein is required for this transport the movement is describe as being facilitated as in protein facilitated. Such movement can be with a concentration (facilitated diffusion) or instead against a concentration gradient (active transport).
Transport proteins generally are both integral membrane proteins and membrane-spanning proteins (transmembrane proteins) since their job is to facilitate movement from one side of the membrane to the other.