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.
Functions of nitrogen in plants. 1  Nitrogen is an essential element of all amino acids. 2  Nitrogen is also a component of nucleic acids, which form the DNA of all living things and holds the genetic code. 3  Nitrogen is a component of chlorophyll, which is the site of carbohydrate formation (photosynthesis).