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.
Determine percentages of the major active ingredients in the package. N-P-K (Nitrogen- Phosphorus- Potassium) are the 3 most abundant ingredients listed on EVERY fertilizer label. They are always in this order, N-P-K. You will see them on the label as three numbers.