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.
Nitrogen credits for previous crops: 1  Alfalfa (good stand): 70 lb N/A. 2  Alfalfa (poor stand): 40 lb N/A. 3  Snap beans: 20 lb N/A. 4  Peas: 20 lb N/A. 5  Soybeans: 20 lb N/A. 6  All other crops: 0 lb N/A.