Complex biochemical processes, like respiration, are made more efficient in eukaryote cells by compartmentalization into organelles, and in some cases by association with membranes. Much of cellular respiration is specifically associated with mitochondria.

Why compartmentalize? You will find some ideas about this in the notes about membrane structure and function. Imagine if your house was just one HUGE room and the furniture, utensils, appliances, etc. from the kitchen, living room, bathrooms, bedrooms, etc. were all haphazardly found anywhere (We are assuming your house does not actually look like this. If it does, then imagine your mother's house or call her and ask her opinion.) How easy would it be to make dinner or do the laundry, or create some craft? (Again if you have never done any of these thing, you might wnat to call your mom). How quickly could you accomplish the task? Would it be more efficient if thigs were arranged into rooms? Hopefully you get the point...