Bark of a tree is impervious to gases and water

this process is called "phosphorylation." a phosphate bond joins adenosine diphosphate to form adenosine triphosphate.

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.