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Flashcards in Lecture 11 Deck (12):

adenylyl cyclase

converts ATP to cAMP


cyclic AMP (cAMP)

diffuses through the cell and activates a serine/threonine kinase, called protein kinase A,which phosphorylates other proteins


G-protein-linked receptor

consists of a receptor protein associated with a G-protein on the cytoplasmic side.
? The receptor consists of seven alpha helices spanning the membrane.
? Effective signal molecules include yeast mating factors, epinephrine, other hormones, and neurotransmitters.



Plants and animals use hormones to signal at greater distances


ligand-gated ion channel

are protein pores that open or close in response to a chemical signal.



small molecules that bind specifically to a larger molecule


local regulator

? Some transmitting cells release local regulators that influence cells in the local vicinity


protein kinase

Most protein kinases act on other substrate proteins, unlike the tyrosine kinases that act on themselves


scaffolding protein

Rather than relying on diffusion of large relay molecules like proteins, many signal pathways are linked together physically by scaffolding proteins


second messenger

? Pathways initiated by both G-protein-linked receptors and tyrosine-kinase receptors involve small, nonprotein, water-soluble molecules or ions, called second messengers.
? These molecules rapidly diffuse throughout the cell.
? Two of the most important are cyclic AMP and Ca2+.


signal-transduction pathway

The process by which a signal on a cell?s surface is converted into a specific cellular response in several steps called a signal-transduction pathway


tyrosine-kinase receptor

? A individual tyrosine-kinase receptors consists of several parts:
? an extracellular signal-binding sites
? a single alpha helix spanning the membrane
? an intracellular tail with several tyrosines

? When ligands bind to two receptors polypeptides, the polypeptides aggregate, forming a dimer.
? This activates the tyrosine-kinase section of both.
? These add phosphates to the tyrosine tails of the other polypeptide.

? The fully-activated receptor proteins activate a variety of specific relay proteins that bind to specific phosphorylated tyrosine molecules.
? One tyrosine-kinase receptor dimer may activate ten or more different intracellular proteins simultaneously.
? These activated relay proteins trigger many different transduction pathways and responses