It's Test Time

Mood: calm
Music: Wind It Up - Gwen Stefani

Bio test in 1 hour and 19 minutes. I've gone through the lecture notes twice today. Honestly, it doesn't seem that difficult at all. I mean, c'mon! Who doesn't know that a receptor protein (when it binds its ligand) activates a g-protein which in turn activates phospholipase C. Phospholipase C cleaves PIP3 into IP3 and DAG. DAG remains in the inner cell membrane while IP3 goes to ligand-gated calcium channels in the endoplasmic reticulum. IP3 then binds to those channels and thus opens them allowing calcium to flow from the endoplasmic reticulum lumen into the cytosol of the cell. Easy peasy.

The fact that I actually find that shite easy is depressing.

Or how 'bout the receptor tyrosine kinase? When it is activated by binding to its ligand, it activates the Ras-activating protein which in turn activates the Ras protein which exchanges its bound GDP for a GTP instead. It then goes off to activate MAP kinase kinase kinase which phosphorylates MAP kinase kinase which phosphorylates MAP kinase which then goes off to do a multitude of things within the cell.

Ready? Last one, I promise. A beta-adrenergic receptor binds epinephrine. The receptor is activated and it goes on to activate a nearby g-protein. This g-protein activates adenylyl cyclase which is an enzyme that converts ATP to cyclic AMP (cAMP). cAMP activates PKA (protein kinase A) which phosphorylates Glycogen Synthase, thus inactivating it. It also phosphorylates Phosphorylase Kinase into its active form. Activated Phosphorylase Kinase phosphorylates Glycogen Phosphorylase. Glycogen Phosphorylase phosphorylates glycogen, thus breaking it down into glucose.

Don't even get me started on protein synthesis in the endoplasmic reticulum (with special emphasis on how/why some proteins are embedded in the lipid membrane of a cell while others transverse the membrane and yet others are not embedded in a membrane at all.) Then there's all that nifty stuff about different cytoskeletan elements! Woot!