Final answer:
The receptor for nitric oxide, which is guanylyl cyclase, is found within the cytoplasm after nitric oxide easily diffuses through the plasma membrane due to its small and hydrophobic nature, leading to biological effects like vasodilation.
Step-by-step explanation:
The receptor for nitric oxide (guanylyl cyclase) is found within the cytoplasm, where it can bind nitric oxide that has diffused across the plasma membrane. Since nitric oxide is a small, hydrophobic, and gaseous signaling molecule, it can easily diffuse through cell membranes and interact with intracellular receptors like guanylyl cyclase, causing an intracellular response such as the production of cyclic GMP (cGMP), which in turn can lead to vasodilation. Therefore, the correct answer to where the receptor for nitric oxide is found is: a) Plasma membrane, where nitric oxide diffuses through to reach guanylyl cyclase in the cytoplasm.