Carboxyl groups have an electronegative oxygen atom double bonded to a carbon atom. This carbon-oxygen bond is very polar and the fact that its a double bond increases the polarity of the bond.
PEA agar, also referred to as Phenylethyl Alcohol Agar is a medium  used by microbiologists to grow microorganisms. The ingredient that  supplies nitrogen is casein. Making the world better, one answer at a time.
Milorganite is a constant combination of five parts nitrogen, two parts phosphorous and no potassium (5-2-0). It also contains 4 percent iron. Scotts fertilizer contains various combinations of nitrogen, phosphorous and potassium, depending on what you're using it for.