Learn French: La membrane est parsemée de particules. - The membrane is dotted with particles.

In the passive voice, par is typically used for specific, active physical actions. However, verbs expressing a state, condition, or a static result—like being covered, filled, or dotted—use de. Here, the particles aren't actively running around dotting the membrane; they are the dots themselves, describing a static condition.

Could I use avec since the English translation is "with particles"?

No, you should avoid avec here. While English uses "dotted with", French relies on de for passive states of covering or filling. Using avec would sound like the membrane used the particles as a tool to dot something else!

Why is it just de particules and not des particules?

In this construction, de acts as the preposition introducing the passive agent. When talking about an unspecific, plural amount (particles in general), the indefinite plural article des is omitted after the preposition de. If you wrote des particules, it would be interpreted as the contraction of de + les, changing the meaning to "dotted with the specific particles".

Why is there an extra e at the end of parsemée?