AP BIOLOGY

Detailed explanation-1: -Answer and Explanation: Out of the molecules listed above, the one that is not involved in cell-to-cell signalling is option (d) cholesterol.

Detailed explanation-2: -Three Stages of Cell Signaling First, reception, whereby the signal molecule binds the receptor. Then, signal transduction, which is where the chemical signal results in a series of enzyme activations. Finally, the response, which is the resulting cellular responses.

Detailed explanation-3: -There are four basic categories of chemical signaling found in multicellular organisms: paracrine signaling, autocrine signaling, endocrine signaling, and signaling by direct contact.

Detailed explanation-4: -The three stages of cell communication (reception, transduction, and response) and how changes couls alter cellular responses. How a receptor protein recognizes signal molecules and starts transduction.