Correct option is B
The retinal rod cell cGMP-phosphodiesterase has a subunit structure of αβγ₂
- α and β subunits: These are the catalytic subunits. They are responsible for the enzyme's activity, which is the hydrolysis of cGMP.
- γ subunits: These are the regulatory subunits. They act as inhibitors of the enzyme. There are two γ subunits that bind to the α and β catalytic subunits, regulating their activity.
In the dark, cGMP levels are high, keeping sodium channels open in the rod cell. This allows the rod cell to be depolarized. When light enters the eye, it triggers a cascade of events that leads to the activation of the cGMP-phosphodiesterase. This enzyme then hydrolyzes cGMP, which causes the sodium channels to close. This leads to the hyperpolarization of the rod cell, which sends a signal to the brain that light has been detected.
Information Booster:
- This enzyme is activated in the presence of light and plays a critical role in the visual process by affecting ion channels in the cell membrane.
- The enzyme's activity is linked to the closure of cGMP-gated ion channels in rod cells, resulting in hyperpolarization of the cell and a reduction in neurotransmitter release.
- Rod cells are specialized for vision in low-light conditions, and this enzyme's action is central to their function.
