Is this question about chemistry?
In the comments I tried to justify my close vote but after some thought I questioned where we should set the boundary between "chemistry" and "the surroundings". The post clearly involves biochemistry but would require a significant description of regulatory pathways, as a web search for "how are cellular levels of PUFA regulated?" will reveal. Are regulatory pathways a subject for this site? Note I am seeking a broader answer that attempts to describe where this site judges the boundary of acceptable subjects to lie.
If I was too quick to vote to close then I'd like to suggest reopening the question.