The density functional study on the functionalization of zigzag graphene nanoribbon [ZGNR(6,0)] was carried out by using the amino acids L-Serine and L-Valine with/without O-2 molecule. Valine is an essential amino acid with hydrophobic character; Serine is a non-essential amino acid with polar nature. The functionalized systems were named as ZGNR-Ser, ZGNR-Val, ZGNR-SerO(2), ZGNR-ValO(2) respectively. The structural stability was analyzed by taking the difference in total energy between the pre and post optimized structures until the change comes to be of the order of 10(-2) to 10(-3) eV. The optimization was performed by using the local density approximation (LDA) with a k-points sampling of 1x1x150. The electronic properties were studied by using the partial charges, chemical potential, electrostatic field, electrostatic strain, static dielectric constant, the density of states, and band structure analysis. A direct relation between electrostatic energy and total energy was observed in all the systems. The band structure results envision that the ZGNR-SerO(2), ZGNR-ValO(2) systems show a semiconducting behavior, whereas the ZGNR-Ser, ZGNR-Val systems show a metallic behavior. The chemical potential analysis suggests a blue shift for the ZGNR-SerO(2), ZGNR-ValO(2) in comparison to the non-oxygen counterparts. The present study indicates the possibility of tuning the electronic properties through covalent functionalization using the amino acids and O-2 molecule and enunciates the option of using them in bioimaging, drug delivery, or theranostic applications.