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.
As an example I will tell you how to extract DNA from peas. 1. Blender insanity. The blender separates the pea cells from each other, so you now have a really thin pea-cell soup. 2. Soapy peas. 3. Enzyme Power.