Final answer:
Hormones bind to specific receptors on target cells. This is similar to how antibiotics bind to specific microbial targets and how neurotransmitters bind to specific receptors in the brain.
Step-by-step explanation:
Hormones mediate changes in target cells by binding to specific hormone receptors. In this way, even though hormones circulate throughout the body and come into contact with many different cell types, they only affect cells that possess the necessary receptors. Receptors for a specific hormone may be found on many different cells or may be limited to a small number of specialized cells. The number of receptors that respond to a hormone determines the cell's sensitivity to that hormone, and the resulting cellular response.
Similar to how hormones bind to specific receptors, antibiotics bind to specific microbial targets. For example, penicillin binds to a specific enzyme found in bacterial cell walls, preventing it from forming and causing the bacteria to die. This selective binding is crucial for the effectiveness of antibiotics.
Another example is how neurotransmitters bind to specific receptors in the brain. Serotonin, for instance, binds to serotonin receptors, which regulate mood and behavior. This targeted binding allows neurotransmitters to modulate signals and influence the functioning of the brain.