Why is it significant that all biological systems use l-amino acids and d-sugars?

L-amino acids and D-sugars are part of every protein.
All proteins are made up of them.
The fact that all biological systems use L-amino acids and D-sugars is linked with the idea that certain groups of organisms come from a common ancestor because. The reason is that if the common ancestors used L-amino acids and D-sugars, than its offsprings use them as well.

Molecules called lipids have long hydrocarbon chains that determine the way they act. they can be fats, oils, or hormones, and even exist in our cell membranes