A penicillin reaction is a life-threatening event. In those who are allergic to penicillin, the drug acts as a that binds to blood proteins, causing a strong immune response.

A penicillin reaction is a life-threatening event. In those who are allergic to penicillin, the drug acts as a hapten that binds to blood proteins, causing a strong immune response.

Explanation:

Low molecular weight chemicals can bind to antibodies, but cannot activate B lymphocytes by themselves (they are not immunogenic). To generate specific antibodies to these small chemicals, immunologists typically bind them to macromolecules prior to immunization. In these cases, the chemical is called a hapten. Penicillin G is a typical hapten that tends to covalently bind to lysine residues both in solution and in protein-bound cells. Penicillin is a drug that behaves as a hapten, since the beta-lactam ring under physiological conditions opens and reacts with the lysine residues of proteins, forming a complex that is the main antigenic determinant of penicillin and other beta-lactams and is capable of to stimulate responses mediated by antibodies or by T cells.

thinking it would be physical characteristics

igneous rocks are formed by solidification of cooled magma (molten rock), with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks.  

the composition depends on the source magma. there are almost a thousand types of composition found till now.  

hope this