Receipt of extracellular signals can change cell behavior quickly (e. g., in seconds or less) or much more slowly (e. g., in hours).

A. What kind of molecular changes could cause quick changes in cell behaviour?

B. What kind of molecular changes could cause slow changes in cell behaviour?

C. Explain why the response you named in A results in a quick change, whereasthe response you named in B results in a slow cha"

A. Molecular changes such as extracellular signals on extracellular ligands can result in quick changes in cell behaviour. One example is insulin. Upon insulin binding on the receptor on the cell membrane, the cell release GLUT4 transporters (for muscle cells) to increase uptake of glucose.

B. Slow changes in cell behaviour can be observed for other lipophilic hormones or intracellular receptors such as glucocoortoid or estrogen which reacts with receptors in the cells.

C. Insulin is required to maintain a constant blood glucose level and hence levels of insulin has to be mediated in correspondence to the blood glucose levels. Fast acting signalling is thus required for homeostasis of blood glucose levels. Where for such lipophilic hormones such as steriods, glucocortoid, these hormones tend to have a longer lasting effect and hence results in a slow change.