Definition is a rhetorical mode that can be used in something smaller or shorter than a full paper. You can use extended definition for several paragraphs only in a paper of much greater length. You also can add to a paper a one-paragraph definition--like a brief encyclopedia definition.
The research group, headed by Dr. Lukas Sommer at the Swiss Federal Institute of Technology, has identified a heretofore unknown role for the TGF cell-to-cell signaling pathway in the pathogenesis of DiGeorge syndrome.
The above image from CestÃ¨le and Catterall in 2000, shows that site 1 of the sodium channel is affected by saxitoxin exposure. It is stated that amino acids E942 and E945 are the affected groups. Saxitoxin is considered a pore blocking toxin. This means they block sodium channels from the extracellular side of the cell. Receptor site 1, is responsible for sodium conductance, therefore, when saxitoxin binds to this site, conductance is diminished (CestÃ¨le and Catterall, 2000).