Which protein associated with sugars helps keep plant cells tightly bound?

Glycoproteins play a crucial role in maintaining the structure and integrity of plant cells by facilitating adhesion and communication between them. These proteins are composed of a protein backbone with carbohydrate (sugar) molecules attached, which contribute to their function in cell-cell recognition and binding. In plants, glycoproteins are often found in the cell wall and play a vital role in stabilizing cell structures, thus ensuring that cells are tightly bound together.

While collagen and elastin are important proteins in animal tissues, and keratin is found primarily in protective structures like hair and feathers, these proteins are not involved in the binding of plant cells. Therefore, glycoproteins are specifically adapted for the structures and functions needed in plants, which is why they are the correct answer in the context of this question.