Final Answer:
Stimulation of rhodopsin by light causes A) the opening of nonspecific cation channels.
Step-by-step explanation:
Rhodopsin Stimulation: The correct option is "a. opening of nonspecific cation channels." When rhodopsin, a light-sensitive receptor in the retina, is stimulated by light, it undergoes a conformational change.
Opening of Nonspecific Cation Channels: This conformational change in rhodopsin leads to the activation of G-proteins and the subsequent activation of phosphodiesterase. As a result, cGMP (cyclic guanosine monophosphate) levels decrease, causing the closure of cGMP-gated sodium channels in the photoreceptor cells.
Decreasing Intracellular Negativity: While rhodopsin activation does impact membrane potential by closing sodium channels, it doesn't directly cause a decrease in intracellular negativity.
Increasing Concentration of cGMP: This is incorrect. Rhodopsin activation actually leads to a decrease in cGMP concentration, which closes the cGMP-gated channels.
In summary, the correct statement is that the stimulation of rhodopsin by light causes the opening of nonspecific cation channels, leading to changes in membrane potential and visual signal transduction.
Stimulation of rhodopsin by light causes A) the opening of nonspecific cation channels.