Phototransduction

Phototransduction is the biochemical conversion of absorbed light into changes in a photoreceptor’s electrical signaling. In vertebrate rods and cones, light lowers intracellular cGMP, closing ion channels and hyperpolarizing the cell.

Rhodopsin: Rhodopsin is the light-sensitive pigment in vertebrate rod cells, composed of opsin and retinal. Its light-triggered shape change initiates the rod phototransduction cascade.
Photoreceptor: A photoreceptor is a sensory cell that detects light and converts it into biological signals. Rods and cones are the cells in which vertebrate phototransduction occurs.
Cone cell: A cone cell is a retinal photoreceptor specialized for color vision and function in bright light. Cones use related phototransduction machinery but differ in sensitivity, speed, and pigment types.
Electroretinography: Electroretinography records electrical responses of the retina to flashes or patterns of light. Its waveforms reveal functional changes in photoreceptors and downstream retinal circuits.
11-cis-retinal: 11-cis-retinal is a vitamin A-derived chromophore that absorbs light and isomerizes to all-trans-retinal. Its isomerization is the first molecular event after photon absorption.
G protein-coupled receptor: A G protein-coupled receptor is a membrane protein that activates intracellular G proteins in response to a signal. Rhodopsin is a light-sensitive member of this receptor family.
Rod cell: A rod cell is a retinal photoreceptor specialized for dim-light vision and high sensitivity. Rods provide the canonical highly amplified vertebrate phototransduction cascade.
Retinitis pigmentosa: Retinitis pigmentosa is a group of inherited retinal disorders that cause progressive photoreceptor degeneration. Mutations affecting phototransduction proteins can disrupt signaling and contribute to retinal degeneration.
Transducin: Transducin is a heterotrimeric G protein activated by light-stimulated rhodopsin. It carries the activated pigment’s signal to phosphodiesterase.
Second messenger: A second messenger is a small intracellular molecule that relays signals from receptors to cellular targets. Cyclic GMP carries the cascade’s signal from phosphodiesterase activity to ion channels.

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