Signalling

Question 1

a) What sort of channel is the Glutamate NMDA (N-methyl D-aspartate) receptor
b) Where does N-glycosylation of nascent proteins occur
c) Function of signal peptidases in the ER lumen
d) What does the SRP bind to
e) When is the SRP released

Answer 1

a) Ligand-gated ion channel
b) Occurs on the side chain NH2 groups of asparagines
c) Cleave signal sequences of proteins destined for secretion
d) Binds simultaneously to the ER signal sequence of a polypeptide and to the ribosome
e) Released as the ribosome is passed to a protein translocation channel in the ER membrane

Question 2

a) What happens when cyclic AMP (cAMP) binds to the regulatory subunits of PKA
b) What is PDK-1 directly activated by
c) What subunits is protein kinase A composed of
d) What sort of channel is the glutamate kainate receptor
e) What is a physiological activator of guanylyl cyclase

Answer 2

a) The catalytic subunits dissociate and become active
b) PIP3
c) Both catalytic and regulatory subunits
d) Ligand-gated ion channel
e) Nitric oxide (NO)

Question 3

a) What type of channel is GABA (gamma-aminobutyric acid)-A receptor
b) What do heterotrimeric G-proteins associate with
c) What is protein kinase B activated by
d) What sort of receptor is the glucagon receptor
e) What is the second messenger whose cellular concentration is decreased when the trimeric G-protein Gi is activated

Answer 3

a) Ligand-gated ion channel
b) Associate with the activated receptor
c) PIP3
d) Coupled to geterotrimeric G-proteins
e) 3’, 5’ cyclic AMP

Question 4

a) What is the substance whose entry into the cell is increased when nicotinic acetylcholine receptors are activated and which causes depolarisation
b) What is the substrate for the enzyme guanylyl cyclase
c) What is the substance that is the immediate precursor of IP3
d) What is the substance whose concentration inside the cell afetr activation of GABA-A receptors
e) What is the substance whose concentration increases inside the cell in response to nitric oxide

Answer 4

a) Sodium ions
b) GTP
c) Phosphatidylinositol-4,5-bisphosphate (PIP2)
d) Cl-
e) 3’,5’ cyclic GMP

Question 5

a) What substance is bound to the α subunit of a trimeric G-protein when it is in its activated state
b) What is the major second messenger generated by activation of insulin receptors
c) What substance regulates protein kinase A
d) What substance increases in concentration in the cytoplasm as a consequence of IP3 generation

Answer 5

a) GTP
b) Phosphatidylinositol trisphosphate (PIP3)
c) 3’-5’-cyclic AMP
d) Calcium ions