hello everybody so today we get to start on lecture number two in the course we're going to talk about how things get in and out of the cell in the last lecture we talked about homeostasis and really in order to deal with homeostasis we had to think about defining fluid compartments in the human body because our definition of homeostasis was the maintenance of a relatively constant internal environment and we defined that internal environment as the extracellular fluid in your body today we're going to look at the single most uh critical structure that mediates the movement or communication or action between fluid compartments between the extracellular fluid and the intracellular fluid so just in case you don't know what the topic of today's lecture is think about that for a second what structure mediates interaction between extracellular fluid and intracellular fluid there's one structure that you should know because you've rocked the general bio already the one thing that separates intracellular fluid the inside of the cell from extracellular fluid the outside of the cell is the cell membrane and today we're going to look at many different ways that the cell membrane carries out this task keeping some stuff out allowing some stuff in allowing some stuff in like investing in getting stuff in or um investing in creating concent ation gradients that let you get other things in it's uh really no surprise human physiology is just so freaking cool so think about the cell for a minute um this video if you have not seen this video it's put together by this x Vivo group and they did this animation of actual cellular processes that is mind-blowing the three minute version has beautiful music makes me cry every time I try not to get too excited I'm not actually going to show it to you here because um you really should go watch it so that you can cry in peace and I won't cry in front of you um but I found an 8 minute version what where they actually narrate the entire process which by the end of the semester you guys are actually going to understand some of the processes that are happening here which is really cool um okay so let's get started let's do a quick review view on the cell membrane like what what is the cell membrane what's its structure and how does it carry out its task of keeping the intracellular fluid separate from the extracellular fluid um so that the cell can function