Question

Is it accurate to say penicillin is an antibody (not just an antibiotic) ?

Answer 1

no.
penicillin is a small molecule. a beta lactam - meaning its core structure is of a two adjoining carbon cycles. one with 6 carbons and one with five.
an antibody - is a macromolecule with a 2 variable which are located in the arms of the Y shape, known as Fab. and a constant "stem". this is the basic unit of an antibody. it can come in a pair - IgA, a quintet - IgM , or alone - IgG (lets forget Ige for a minute).
the fact the penicllin targets like a smart bomb if ull like bacterial cell wall machinery - does not confer it antibody-ness

Answer 2

So you're basically saying that penicillin isn't an antibody because of they've got totally different chemical structures and kills germs, or bacteria, for its own different reasons?