Question 28 of 41 incorrect X Map deb sapling Phototransduction uses a signal tr

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Question 28 of 41 incorrect X Map deb sapling 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 transducin dissociates into Ta-GTP and T cGMP PDE converts cGMP 11-cis-retinal converted to all-trans-retinal to biologically inactive 5-GMP cGMP-gated ion channels close high (ca linhibits guanylyl cyclase Ta subunit encounters PDE [Ca declines GDP bound to transducin Ta subunit hydrolyzes GTP guanytyl cyclase (cGMP) decreases PDE bound to inhibitory subunit converst GTP to cGMP Hint Previous Give Up & View Solution Check Answer Next Exit about us careers. partners privacy policy terms of use conta

Explanation / Answer

Phototranduction increase:

1.  11-cis-retinal to converted to all trans retinal c-GMP gated ion channels closed.

2. T alpha subunit encountering PDE decline Ca+ ions.

3. Transducin, (G-protein) dissociate into G alpha-GTP and G beta gamma subunits.

4. G alpha subunit hydrolyse GTP.

5.

Phototransduction donot increase:

1. G alpha subunit hydrolyse GTP. (G alpha -GTP to G alpha GDP)

2. High Ca+ ions decrease guanylyl cyclase.

3. GDP bound to transducin

In phototransduction Receptor is rhodopsin, G proteins is transducin and effector is cGMP Phosphodiesterase (PDE).

Phototransduction cascade begins with absorption of photons by phoreceptor pigments, rhodopsin isomerising 11-cis-retinal to all trans retinal.This causes conformational change in rhodopsin to Meta II state that catalyses exchange of GDP for GTP on trimeric G-protein

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