How do cells respond to external signals?

Cells respond to external signals through a process called signal transduction, which involves reception, transduction, and response.

Cells are constantly communicating with their environment and each other, and this communication is vital for their survival and function. This communication is facilitated by external signals, which can be physical (like light or touch) or chemical (like hormones or neurotransmitters). These signals are detected by cells through a process called signal transduction.

Signal transduction begins with reception. The external signal, or ligand, binds to a specific receptor on the cell surface. These receptors are usually proteins and are specific to the type of signal they can bind to. This binding event triggers a change in the receptor's shape, which allows it to interact with other molecules inside the cell.

The next step is transduction. This is where the signal is converted into a form that can bring about a specific cellular response. This often involves a series of steps, each catalysed by a different molecule. These molecules are often proteins, and the series of steps they catalyse is known as a signal transduction pathway. Each step in the pathway amplifies the signal, meaning a single ligand-receptor interaction can result in a large cellular response.

Finally, the signal triggers a specific cellular response. This could be anything from gene expression to cell division, depending on the type of signal and the specific cell type. The response is often mediated by 'effector' proteins, which carry out the final step in the signal transduction pathway.

In summary, cells respond to external signals through a process of reception, transduction, and response. This process allows cells to sense and respond to their environment, ensuring they can adapt to changes and carry out their functions effectively.