Photoreceptor proteins are specialized molecules found in various organisms that detect light and convert it into biochemical signals. They play a crucial role in processes such as vision in animals and photosynthesis in plants. Common types of photoreceptor proteins include rhodopsins, which are involved in vision, and phytochromes, which help plants sense light conditions. These proteins contain chromophores, which are light-absorbing components that change shape when they absorb photons. This structural change triggers a cascade of reactions within the cell, leading to physiological responses. Photoreceptor proteins are essential for adapting to light environments and regulating biological functions.