Which type of feedback loop can create memory in cells?

A positive feedback loop can create memory in cells because it amplifies a response in a way that reinforces a particular state or function. In biological systems, this means that when a certain threshold is reached, the process encourages further progression in the same direction. The classic example is during processes like the activation of certain genes or signaling pathways, where an initial stimulus results in an accumulation of products that further stimulate the process.

This amplification can lead to self-sustaining states, where the cellular system "remembers" its past condition. For instance, once a cell has committed to a differentiation process, the positive feedback can help maintain that state even in the absence of the initial signals, effectively allowing the cell to "remember" the event that triggered differentiation.

While negative feedback loops help stabilize biological systems by counteracting changes and restoring homeostasis, they do not create memory in the same way that positive feedback loops do. Indirect positive feedback loops and feed-forward loops may also play roles in cellular responses but are not as directly linked to the concept of cellular memory as a straightforward positive feedback loop is.