An effector is some type of molecule. It could be an enzyme, it could be a protein pump, it could be a membrane channel or it could be some type of transcription inducing molecule. So basically, these effectors are actually themselves responsible for carrying out some type of specific process that takes place inside the body. And all these processes basically work together to carry out that specific physiological response. So effectors are molecules that are responsible for carrying out some type of cellular process that ultimately leads to that physiological response. And effectors can be transcription inducing molecules, enzymes.