lectin

n. any of a number of plant proteins that bind to particular carbohydrates (Biochemistry)

Lectins are carbohydrate-binding proteins or glycoproteins which are highly specific for their sugar moieties.
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Lectin /lec·tin/ any of a group of hemagglutinating proteins found primarily in plant seeds, which bind specifically to the branching sugar [more]Lectin - Community and Resources

Noun
1. any of several plant glycoproteins that act like specific antibodies but are not antibodies in that they are not evoked by an antigenic stimulus
(hypernym) glycoprotein

A complex molecule that has both protein and sugars. Lectins are able to bind to the outside of a cell and cause biochemical changes in it. Lectins are made by both animals and plants.