Question

compounds considered to be growth factors ______. can be synthesized by the cell enter the cell by diffusion are usually hydrophobic are acquired from the environment

Explanation:

Growth factors are signaling molecules that cells cannot synthesize on their own; they must obtain these compounds from their surrounding environment to support cell growth, proliferation, and differentiation. The other options are incorrect: cells cannot synthesize their own growth factors, most growth factors are hydrophilic (so they do not enter via simple diffusion, instead using receptor-mediated uptake), and they are not hydrophobic.

Answer:

D. are acquired from the environment