Red bone marrow cells respond to a hormone called erythropoietin. Why doesn't a liver or kidney cell respond to this hormone?
a. The hormone is water-soluble, so kidney and liver cells cannot respond to it.
b. Only hormones secreted by the bone marrow are able to act upon the bone marrow.
c. Ion channels that allow erythropoietin to diffuse into the cell are missing in kidney and liver cells.
d. Kidney and liver cells do not contain the protein receptor that binds erythropoietin.
