gpcrs

Question 1

characteristics and features of signal transduction

Answer 1

contact dependent, secreted molecules
general features= specificity, sensitivity, amplification, modularity, desensitization & integration, localized response

Question 2

G-protein coupled receptors

Answer 2

B-andregenic receptor, G protein, second messenger signaling, protein kinase, regulation and desensitization

Question 3

general features of signal transduction

Answer 3

a signal (ligand) interacts with a receptor, activated receptor interacts with cellular machinery to produce a second signal or a change in protein activity, cellular metabolic activity changes, transduction event ends

Question 4

two types of intercellular signal transduction

Answer 4

1)contact-dependent
2) secreted molecules
-> paracrine
-> endocrine
-> autocrine
-> synaptic

Question 5

types of secreted signaling molecules

Answer 5

AAs, proteins, glycoproteins, small peptides, amines, lipids, nucleotides/nucleosides, gases

Question 6

specificity

Answer 6

achieved by precise molecular complementarity between the signal and receptor molecules- mediated by weak (noncovalent) forces

Question 7

amplification

Answer 7

results when an enzyme is activated by a signal receptor and in turn catalyzes the activation of many molecules of a second enzyme, & so on, in an enzyme cascade

Question 8

modular

Answer 8

has multiple domains that recognize specific features- allows cells to mix and match a set of signaling molecules; phosphorylation provides reversible points of interaction

Question 9

scaffold proteins

Answer 9

nonenzymatic proteins that bring together enzymes that interact in cascades

Question 10

desensitized

Answer 10

no longer responsive to a signal- occurs when a signal is present continuously

Question 11

integration

Answer 11

ability of the system to receive multiple signals & produce a unified response

Question 12

response localization

Answer 12

cells confine signaling system components to a structure to regulate processes locally

Question 13

first messenger

Answer 13

extracellular signal

Question 14

second messenger

Answer 14

metabolite or ion

Question 15

which statement describes the active form of the guanosine nucleotide-binding protein?

Answer 15

GTP binds the a subunit

Question 16

G-protein coupled receptor

Answer 16

external ligand binding to receptor activates an intracellular GTP-binding protein, which regulates an enzyme that generates an intracellular second messenger

Question 17

receptor enzyme (tyrosine kinase)

Answer 17

ligand binding activates tyrosine kinase activity by autophosphorylation; kinase activates transcription factor, altering gene expression (kinase cascade)

Question 18

B-adrenergic receptor

Answer 18

epinephrine binds to specific receptor; hormone-recept or complex causes the GDP bound to Gsa to be replaced by GTP, activating Gsa; activated Gsa separates from GsB moves to adenylyl cyclase, and activates it. Many GsB subunits may be activated by one occupied receptor; adenylyl cyclase catalyzes the formation of cAMP; cAMP activates PKA; phosphorylation of cellular proteins by PKA causes the cellular response to epinephrine; cAMP is degraded, reversing the activation of PKA