Final answer:
Glycoproteins consist of chains of carbohydrates projecting out of the cell membrane, acting as labels for cell recognition. Proteoglycans are polysaccharide chains covalently linked to proteins, occupying space and forming hydrated gels. Both have carbohydrate components on the cell surface and contribute to the glycocalyx.
Step-by-step explanation:
Glycoproteins consist of a protein in the plasma membrane with chains of carbohydrates projecting out of the cell. They act as labels to identify the cell and aid in cell recognition.
Proteoglycans include polysaccharide chains called glycosaminoglycans (GAGs) covalently linked to proteins. They occupy large amounts of space, form hydrated gels, and resist compression.
Both glycoproteins and proteoglycans have carbohydrate components on the exterior surface of the cell and are collectively referred to as the glycocalyx. The glycocalyx plays a role in cell recognition, interaction with the environment, and cell signaling.