If you have an experiment in which there are 4 different groups, and the same variable is manipulated in all of them, is there a control group?

No

Explanation:I believe it is no due to the fact that the variable is being manipulated in all groups and in order to be a control groups the variable must remain the same or must not be manipulated.

hope this helps :)

hormones in blood stream

image: dtc.ucsf.edu

endocrine glands secrete hormones into the blood stream near them; the hormones then travel in our bloodstream until it reaches its destination, called a target cell, in distance parts of the body. in the target tissue, hormones lock onto the target’s plasma membrane, called the receptor site.