Short, branched oligosaccharides that are attached to proteins are known as what?

Short, branched oligosaccharides that are attached to proteins are specifically referred to as glycoproteins. These glycoproteins play crucial roles in various biological processes, including cell-cell recognition, signaling, and immune responses. The carbohydrates (oligosaccharides) in glycoproteins can influence protein folding, stability, and activity.

Glycoproteins are integral to the structure and function of many proteins found on cell surfaces and in secreted proteins. They often have key roles in the immune response; for instance, many antibodies are glycoproteins, which are critical for recognizing pathogens.

The other options describe different types of biomolecules. Proteoglycans, for example, are a subset of glycoproteins which have much larger glycosaminoglycan chains and are typically found in the extracellular matrix. Glycolipids consist of carbohydrates attached to lipids, primarily found in cell membranes, while phospholipids are components of cell membranes that consist of a glycerol backbone, fatty acid tails, and a phosphate group but do not contain carbohydrate moieties. Thus, glycoproteins are the correct term for the molecules in question.