 Now the smooth endoplasmic reticulum is also an extension of the nuclear envelope. So take a look at this picture here and where do you think the smooth endoplasmic reticulum is? Right there. And look at it. Do you see how my little purple ribosomes that are like embedded all over this maze of rough endoplasmic reticulum. Where are they? They're totally lacking. My little light blue-greenish dots that are inside the maze, those are still present. They're not the same thing. What would you think they would be in the rough endoplasmic reticulum? They're proteins because proteins are being processed in the rough ER. There's smooth ER in general. The general conclusion that we can draw is that smooth endoplasmic reticulum is involved in processing not proteins, but smooth ER processes fats. So it's basically, it does this exact thing. It modifies and processes fats because cells sometimes produce fats for a purpose, like sometimes, for example, in making breast milk. You want to send fat to your kid that is latched onto you like a little parasite. So yeah, send some fat out there and your system better produce some fats to give to your little parasite that's attached to your nipple. So there are several examples where the body actually produces fats to release out into the system to carry out some sort of function. Cholesterol, steroid hormones have to be produced somewhere and the smooth endoplasmic reticulum plays a role in processing those fats to do the job that the cell is assigned to carrying out. Did you understand what I just said? Of course you did, but I say generally that's its job. The crazy thing is the smooth endoplasmic reticulum has different jobs depending on where it is. So for example, in your liver, when you get a wild hair and decide, oh, this weekend it would be really fun to drink yeast pee and poison my liver, your liver says, bring it, bring it, son, because I'm going to detox that poison that you are putting into me using my smooth endoplasmic reticulum. What? Smooth ER in the liver detoxes alcohol. That's part of why your liver can be severely damaged by repeated yeast pee poisoning. Don't forget, alcohol is nothing more than yeast pee. So every time you want to party in the weekend, when you're drinking yeast pee, don't forget that. You're drinking yeast pee and poisoning your poor little liver that's just trying to process it and keep the rest of your body safe. Smooth ER in skeletal muscle is involved in storing calcium and it stores it up inside the smooth ER. It's not processing fat anymore and it's not processing alcohol. It's storing calcium and it allows the calcium when your body says, please contract skeletal muscle. The smooth ER barfs out all of that calcium that it was storing out and the calcium is necessary to initiate a muscle contraction. The smooth ER in skeletal muscle is covered with transporters, which is the topic of our next lecture. Those transporters put the calcium back into the smooth and the plasma reticulum for the next time that the muscle is ordered to contract. So depending on where you are, smooth ER might have different functions. But if we were to say, okay, what's the general function of smooth ER? It's to process fats. We've processed proteins in the rough ER. We've processed fats in the smooth ER. The next structure is actually going to package these things. They've been processed and now it's time to package them.