Variations in the covalent alteration of one or more components (eg: fatty acids, sterols etc.) in a lipid, resulting in a change in the properties of the lipid, compared to control.
Any variation in a series of molecular signals that help relay a receptor mediated signal within the cell, compared to control. Second messengers often comprise of ions (eg: Ca2+) or small molecules (cGMP, cAMP etc) that are formed or released into the cytosol.