protopectin
/ˌprəʊtə(ʊ)ˈpɛktɪn/Biochemistry
noun
A water-insoluble pectic substance containing glucuronic acid monomers, which is present as a binding substance between plant cell walls, and which breaks down during the ripening of fruits and fleshy roots, giving rise to pectin.
Origin
Early 20th century; earliest use found in Chemical Abstracts. From proto- + pectin, after German Protopektin.