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.
What fertilizer nutrient balance to choose for tomatoes. Nitrogen. Nitrogen encourages leaf growth, which is why fertilizers with higher ratio of nitrogen (the first of the three numbers) are an optimum choice for lawns and grasses.