Phototransduction uses a signal transduction cascade similar to mechanisms stimu
ID: 60946 • Letter: P
Question
Phototransduction uses a signal transduction cascade similar to mechanisms stimulated by hormones and neurotransmitters. However, the visual sensory apparatus is stimulated by photons, and converts light energy into a nerve impulse. Determine whether each of the the following events increases phototransduction or does not increase phototransduction (either by not initiating a signal or by terminating the signal). The abbreviation cGMP is used for guanosine 3',5'-cyclic monophosphate (cyclic GMP), and PDE is used for phosphodiesterase.
Phototransduction uses a signal transduction cascade similar to mechanisms stimulated by hormones and neurotransmitters. However, the visual sensory apparatus is stimulated by photons, and converts light energy into a nerve impulse Determine whether each of the the following events increases phototransduction or does not increase phototransduction (either by not initiating a signal or by terminating the signal). The abbreviation cGMP is used for guanosine 3',5'-cyclic monophosphate (cyclic GMP), and PDE is used for phosphodiesterase. Phototransduction increases Phototransduction does not increase CGMP-gated ion channels close high [Ca2t] inhibits guanylyl cyclase transducin dissociates into TarGTP and TB SDP bound to transducin PDE bound to inhibitory subunit [Ca2] declinesuanyyl gyclase 11-cis-retinal converted to all-trans-retinal Ta subunit encounters PDE [cGMP decreases Ta subunit hydrolyzes GTP CGMP PDE converts cGMP guanylyl cyclase converst GTP to cGMP Caf declines to biologically inactive 5'-GMFP Previous Check Answer-Next Exit Hint Phototransduction is triggered by light (photons). Cyclic GMP concentration affects ion channels to bring about either depolarization or hyperpolarization. Consider whether a high or low [cGMP] opens or closes ion channels that permit the influx of Na* and Ca2*Explanation / Answer
11-cis-retinal converted to all-trans-retinal,
transducin dissociates into T-alpha GTP and Tbeta &gamma
T -alpha subunit encounters PDE,
Guanyl cyclase converts GTP to cGMP,
cGMP PDE converts cGMP converts cGMP to biologically active 5'-GMP
[cGMP] decreases,
cGMP- gated channel close,
Ca2+ declines.
GDP bound to transducin,
T-alpha hydrolyzes GTP,
high Ca2+ inhibits guanyl cyclase,
GDP bound to transducin.
Phototransduction increases Phototransduction decreases11-cis-retinal converted to all-trans-retinal,
transducin dissociates into T-alpha GTP and Tbeta &gamma
T -alpha subunit encounters PDE,
Guanyl cyclase converts GTP to cGMP,
cGMP PDE converts cGMP converts cGMP to biologically active 5'-GMP
[cGMP] decreases,
cGMP- gated channel close,
Ca2+ declines.
GDP bound to transducin,
T-alpha hydrolyzes GTP,
high Ca2+ inhibits guanyl cyclase,
GDP bound to transducin.