I decided to include these terms because they are used so commonly in science writing, and because even though the spell checker and grammar checker do not distinguish between them, the thinking student obviously must do so. "Absorb," which describes a general process, means "to soak in." A more specialized term, "adsorb" describes the surface of a solid or liquid accumulating gas, vapor, or dissolved matter:
This product claims to absorb excess dietary fat.
Once the bacteria adsorb to the aluminosilicate mineral surface, they secrete organic molecules.