Phototransduction uses a signal transduction cascade similar to mechanisms stimu
ID: 60547 • 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.
(Sort between Phototransduction increases AND Phototransduction does not increase)
PDE bound to inhibtory subunit,
Guanylyl cyclase converst GTP to cGMP
[Ca2+] declines
11-cis-retinal converted to all-trans-retinal
T(alpha) subunit encounters PDE
[cGMP] decreases
GDP bound to tranducin
T(alpha) subunit hydrolyzes GTP
transducin dissociates into T(alpha)GTP and T(beta/gamma)
high [Ca2+] inhibits Guanylyl cyclase
cGMP PDE converts cGMP to biologically inactive 5'-GMP
cGMP-gated ion channel close
PLEASE MATCH ALL with either (Phototransduction increases or Phototransduction does not increase)
Explanation / Answer
PDE bound to inhibitory subunit - Phototransduction decreases
Guanylyl cyclase converts GTP to cGMP – Phototransduction decreases
Ca2+ declines - Phototransduction increases
11- cis-retinal converted to all-trans-retinal – Phototransduction increases
T (alpha) subunit encounters PDE – Phototransduction increases
(cGMP) decreases – Phototransduction increases
GDP bound to transducin – Phototransduction decreases
T (alpha) subunit hydrolyzes GTP - Phototransduction decreases
Transducin dissociates into T (alpha) GTP and T(beta/gamma) - Phototransduction increases
High (Ca2+) inhibits Guanylyl cyclase – Phototransduction decreases
cGMP PDE converts cGMP to biologically inactive 5’-GMP - Phototransduction increases
cGMP-gated ion channels close - Phototransduction increases.