What does it mean to say that a signal is transduced?
a. The signaling molecule enters the cell directly and elicits a cellular response.
b. The signal is generated by the production of proteins.
c. The physical form of the signal changes between the outside of the cell and the inside.
d. The signal is amplified.

Signal transduction refers to the process by which a cell converts an external signal into a functional response. This involves a series of molecular events, often including the activation of proteins and second messengers, that lead to changes in cellular activity. The signal's physical form may change as it is relayed from the cell surface to the interior.

A cellular response is the outcome of signal transduction, where the cell reacts to a signal by altering its behavior or function. This can include changes in gene expression, enzyme activity, or cell movement. The response is specific to the type of signal received and the pathways activated within the cell.

Signal amplification is a process within signal transduction where the initial signal is strengthened, allowing a small number of signaling molecules to produce a large cellular response. This is achieved through cascades of enzymatic reactions, where each step amplifies the signal, ensuring an effective and robust response to external stimuli.