A/N: Science nerdery ahead! Feel free to skip this chapter if you don't like such things. If you want to know what these abbreviations mean, check out the Wikipedia article on the MAPK/ERK pathway. Phosphorylation is the attachment of a phosphate group to a molecule, and a kinase is an enzyme that phosphorylates things. And now you know everything I remember from biochem. :)
Few people on Earth can be as melodramatic as medical students at 2 AM during exam week. Mike is convinced that he'll never learn the cell signaling pathways by tomorrow and will face ignominy and failure. John does his best to reassure him.
"You can do this. Let's start from the beginning of the pathway: the extracellular ligand binds to the EGFR, and then…"
The bespectacled man starts out fluently and then deteriorates. "The tyrosine kinase is activated, and then EGFR is phosphorylated. The GRB2-SOS complex is formed and then… uh…"
"Something we both want to do right now," John says, not unkindly.
"Activates SOS! Yes, then SOS takes a GDP off of Ras, which activates it. Ras then binds to, er…" Mike paused, struggling again.
John smiles slightly. "Think of those nancies in blue…"
"RAF! Then RAF phosphorylates MEK, and MEK phosphorylates MAPK."
John grins. "Well done. Only five more pathways to go."
"Yes, and after that we'll get on to pathology. The student shall become the teacher," Mike says with a twinkle in his eye.
The blond man groans and rests his head on the desk, and not just because Mike's impression of Bruce Lee is the worst he's ever heard. (Pathology is a trick to lower everyone's grades except Mike's.) John's greatest fear is that he'll flunk out.