What happens to a photoreceptor cell that loses the function of all of its cGMP phosphodiesterase?

What happens to a photoreceptor cell that loses the function of all of its cGMP phosphodiesterase?

• A. The rhodopsin GPCR of the photoreceptor cell will have diminished sensitivity to light
• B. The rhodopsin GPCR of the photoreceptor cell will have increased sensitivity to light due to loss of adaptation
• C. The rhodopsin GPCR of the photoreceptor cell will have diminished sensitivity to light due to adaptation
• D. The rhodopsin GPCR of the photoreceptor cell will have increased sensitivity to light due to negative feedback regulation

Answer: (B)

A photoreceptor cell that loses the function of all its cGMP phosphodiesterase would lead to a significant accumulation of cGMP within the cell. In normal functioning, cGMP phosphodiesterase breaks down cGMP, and this process is essential for the phototransduction cascade that converts light signals into electrical signals in the retina. Rhodopsin, the light-sensitive GPCR in photoreceptor cells, is activated by photons of light, which typically leads to a series of biochemical reactions resulting in the closure of cGMP-gated ion channels. This closure contributes to the hyperpolarization of the cell, resulting in decreased neurotransmitter release to bipolar cells. When cGMP phosphodiesterase is not functioning, cGMP levels remain high, keeping the cGMP-gated channels open. The prolonged opening of these channels prevents the cell from adequately hyperpolarizing and fully responding to light stimuli. As a result, without the ability to adapt effectively, the sensitivity to light increases because the photoreceptor remains in a state that does not allow for proper signal processing in response to varying light levels. Hence, the cell experiences heightened sensitivity due to the loss of adaptation; it cannot properly adjust to bright

A photoreceptor cell that loses the function of all its cGMP phosphodiesterase would lead to a significant accumulation of cGMP within the cell. In normal functioning, cGMP phosphodiesterase breaks down cGMP, and this process is essential for the phototransduction cascade that converts light signals into electrical signals in the retina.

Rhodopsin, the light-sensitive GPCR in photoreceptor cells, is activated by photons of light, which typically leads to a series of biochemical reactions resulting in the closure of cGMP-gated ion channels. This closure contributes to the hyperpolarization of the cell, resulting in decreased neurotransmitter release to bipolar cells. When cGMP phosphodiesterase is not functioning, cGMP levels remain high, keeping the cGMP-gated channels open. The prolonged opening of these channels prevents the cell from adequately hyperpolarizing and fully responding to light stimuli.

As a result, without the ability to adapt effectively, the sensitivity to light increases because the photoreceptor remains in a state that does not allow for proper signal processing in response to varying light levels. Hence, the cell experiences heightened sensitivity due to the loss of adaptation; it cannot properly adjust to bright