Receptors and Cell Signaling

Question 1

Endocrine Signaling

Answer 1

Hormones transported via blood; long distance and long lasting signals

Question 2

Paracrine Signaling

Answer 2

signal (paracrine factor) diffuses to neighboring cells of different types; local signaling in short lived cells; leydig cells to germ and Sertoli cells

Question 3

Autocrine Signaling

Answer 3

secreting cells express the receptor for the signal secreted; common in immunology

Question 4

Direct or Juxtacrine Signaling

Answer 4

Signal binds to signaling cell which then binds the target cell; Heparin binding epidermal growth factor binds to EGF receptor

Question 5

Hydrophilic Signaling

Answer 5

cannot cross plasma membrane; interact with receptors at membrane surface which activate secondary messengers; leads to cellular response; short half lives

Question 6

Lipophilic Signaling

Answer 6

steroids pass through membrane and bind to receptors in cytoplasm or in nucleus; act as transcription factors; long half lives

Question 7

Gs pathway

Answer 7

stimulates adenylate cyclase which makes cAMP and cAMP activates PkA; phosphodiesterase breaks down cAMP to end; insulin bound to beta-andrenergic and histamine

Question 8

Gi pathway

Answer 8

Inhibits adenylate cyclase; epinephrine bound to alpha-adrenergic receptor and dopamine

Question 9

Gq pathway

Answer 9

activates phospholipase C; PLC breaks PIP to DAG and IP3; DAG activates PKC and IP3 goes to ER to open calcium channels; acetylcholine

Question 10

Gt pathway

Answer 10

stimulates cGMP phosphodiesterase which breaks down cGMP to 5’-GMP; activated by photons (light)

Question 11

Receptor desensitizaiton (4)

Answer 11

1. hormone levels drop
2. removal of signaling molecule
3. sequestration of receptor in endosomes
4. sequestration and destruction in endosomes and lysosomes

Question 12

Exist in inactive complex with HSP90; binding causes HSP to dissociate and complex translocates; binds to HRE

Answer 12

Cytoplasmic Receptor

Question 13

Already present in nucleus attached to DNA

Answer 13

Nuclear Receptor

Question 14

Epinephrine bound to beta-andrenergic (Gs) receptor

Answer 14

relaxation of bronchial and intestines; heart contractions; breakdown of glycogen stores (Epi pen)

Question 15

Epinephrine/norepinephrine bound to alpha-adrenergic receptor (Gi)

Answer 15

constriction of smooth muscles

Question 16

toxin keeps Gs-alpha active by decreasing GTPase activity; results in overproduction of cAMP; opens Cl- channels in intestines and H20 moves to compensate

Answer 16

Cholera toxin

Question 17

toxin prevents ADP ribosylation on Cys of Gi-alpha preventing activation; Adenylate cyclase is not inhibited, leading to overproduction of cAMP; loss of fluids and mucous in airway

Answer 17

Pertussis Toxin

Question 18

Phosphorylate GPCRs allowing arrestin to bind 3rd intracellular loop; G-alpha-GDP does not get converted to GTP

Answer 18

G-protein Receptor Kinases (GRKs)