Difference between eukaryotic and prokaryotic cells

The main difference is the presence of a nucleus.

Explanation:

One of the biggest differences is the presence of a nucleus with an envelope. This is very important because in eukaryotes it is present, but in prokaryotes, the genetic material is in the cytosol, although it's not exactly dispersed, it's slightly grouped. Also, the DNA in prokaryotes is organized in circular chromosomes while in eukaryotes it's organized in linear chromosomes arranged in an X shape. There are many more differences, but these two are the more important ones.

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.

a "theory" a suggestion that is not 100 % accurate, or a figure. some people say its a theory because they of all the passed theory's about one subject. it depends sometimes theory might be accurate and sometimes they are.