AP Bio questions

aldfig0
Sun, 23 Oct 2011 02:15:32 +0000

Receptor-mediated endocytosis allows for only specific substances to be taken inside the cell. Pinocytosis doesn’t discriminate like receptor-mediated endocytosis, and thus may take in something else needed by the cells. I don’t think it’s possible for all of the signal molecules to be taken in (some should randomly diffuse everywhere, too far to be caught), but receptor-mediated endocytosis will allow for the particular ligand of interest to be picked up so it won’t cause another response, without interfering with other substances in the surroundings.

A cotransporter by definition allows some substance to use the concentration gradient of something else to enter against its own concentration gradient. The sodium potassium does not fit this definition; it just generates a concentration gradient (to be more precise, it creates an electrochemical gradient).