Final answer:
Pectin, a polysaccharide found in plant cell walls, is essential for producing the gel-like consistency of jams and jellies.
Step-by-step explanation:
The plant cell wall molecule that is economically important as a component essential for the production of jams and jellies is pectin. Pectin is a polysaccharide found embedded in the primary cell wall of plants, within a matrix of other polysaccharides such as cellulose and hemicellulose.
Pectin is highly valued in the food industry due to its ability to gel and thicken, which is crucial for the consistency of jams and jellies. Additionally, pectin is also a form of dietary fiber, which contributes to the cellulose content of food.