Cell Signaling

Question 1

Endocrine

Answer 1

a. Signal is transported via blood
b. Ex: Epiniephrine
c. Long-distance signaling
d. Epinephrine released by adrenal medulla acts on heart muscle
e. Long-lasting

Question 2

Paracrine

Answer 2

a. Signal diffuses to neighboring target cell of a different cell type
b. Ex: testosterone
c. Leydig cells synthesize and secrete testosterone which induces spermatogenesis by acting on Sertoli and germ cells
d. Local signaling
e. Short-lived signal

Question 3

Autocrine

Answer 3

a. Secreting cells express surface receptors for the signal
b. Ex: Interlukin-1
c. Common in chemokines: IL-1 produced by T-lymphocytes promote their own replication during an immune response

Question 4

Juxtacrine

Answer 4

a. Signal binds to signaling cell which then binds to receptor on the target cell
b. Ex: Heparin-binding epidermal growth factor in immune cells

Question 5

Lipophilic

Answer 5

a. Steroids
b. Cytoplasmic receptors
i. Exist in an inactive form complexed with HSP 90
ii. Upon binding to ligand, HSP dissociates
iii. Hormone-receptor complex translocates to nucleus where it binds to a specific DNA sequence called the hormone response element (HRE)
c. Nuclear receptors
i. Already present in nucleus bound to DNA

Question 6

Hydrophilic

Answer 6

a. Insulin
b. Glucagon
c. Signaling molecule-receptor complex initiates production of second messenger molecules inside the cell
d. G Protein-coupled receptors (Epinephrine)
e. Receptor tyrosine kinases (Insulin)

Question 7

how does viagra work?

Answer 7

Inhibits cGMP Phosphodiesterase, which leads to build up of cGMP to prolong smooth muscle relaxation and vasodilation, resulting in an erection

Question 8

Cholera toxin mechanism

Answer 8

c. Colavent modification of alpha subunits of Gs
d. ADP ribosylation of Arg in Gs alpha decreases intrinsic GTPase activity
e. Gs alpha remains active and continuously stimulates adenylate cyclase, resulting in overproduction of cAMP
f. Overabundance of cAMP in intestinal cells open Cl- channels, loss of electrolytes and water, results in diarrhea

Question 9

 Neurofibromatosis

Answer 9

condition marked by growth of tumors in nerve tissue
 Caused by inactiviating mutation in neurofibromin gene, which encodes a GAP for RAS, RAS uncontrollably activated patheays for nerve tissue growth