Final answer:
Signal transduction involves the cell's response to external stimuli, such as specific molecules or light, through a series of molecular events that amplify the signal and lead to a cellular response.
Step-by-step explanation:
Signal transduction involves the response of a cell to external stimuli such as specific molecules or light. The key elements of signal transduction pathways include the reception of a stimulus at a cell-surface receptor, the propagation of the signal through a cascade of molecular events inside the cell, which may involve phosphorylation to activate or inactivate target proteins, and the production of a cellular response. This system allows for the amplification of a signal, where a few signal molecules can lead to a magnified response, and the integration of signals from multiple pathways to activate the same response in a cell.
Moreover, signal transduction is crucial in evolutionary terms, given that organisms have adapted pre-existing signaling systems for new pathways as they evolved, and in humans, it allows for the accurate perception of stimuli like visible light. Different cell types may respond differently to the same signal, demonstrating the complexity and specificity of these pathways.
Therefore, the correct answer in the context of signal transduction is c. involves the response of a cell to external stimuli such as specific molecules or light.