Lecture 11

Question 1

adenylyl cyclase

Answer 1

converts ATP to cAMP

Question 2

cyclic AMP (cAMP)

Answer 2

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

Question 3

G-protein-linked receptor

Answer 3

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.

Question 4

hormone

Answer 4

Plants and animals use hormones to signal at greater distances

Question 5

ligand-gated ion channel

Answer 5

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

Question 6

ligand

Answer 6

small molecules that bind specifically to a larger molecule

Question 7

local regulator

Answer 7

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

Question 8

protein kinase

Answer 8

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

Question 9

scaffolding protein

Answer 9

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

Question 10

second messenger

Answer 10

? 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+.

Question 11

signal-transduction pathway

Answer 11

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

Question 12

tyrosine-kinase receptor

Answer 12

? 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