This is a promotional video for the University of Utrecht, but it doesn’t lie (although I’m beginning to detest the phrase “dark matter of the ______”). Glycans are essential components of the cell.
In our cell biology course — and probably in most cell bio courses — we start with an overview of those key macromolecules, carbohydrates, lipids, proteins, and nucleic acids, and then spend almost all of the semester focused on proteins and nucleic acids. I think in part it’s because we have a straightforward connection between them, and so much of the discipline of molecular biology is about just those two. It’s also the case that there is no such thing as a gene coding for a lipid or a glycan, which immediately removes them from consideration or interest to many biologists. Instead, glycans and lipids are produced indirectly by the cellular and extracellular environment, which makes them an order of magnitude more difficult to understand.
But that should make them even cooler!
It doesn’t make them “dark matter of the cell”, though.