A mortgage is a security interest in real property which secures a mortgage note.
A mortgage note is a promissory note to repay a loan secured by a mortgage.
A mortgage note is not a negotiable instrument and therefore is not covered by UCC § 3.
Mortgages are real estate interests and are perfected by filing the mortgages and associated notes in the county where the property is located.
The only UCC section to apply to mortgages is UCC § 9.