Cell Membranes – Prep Week 4
This is the fourth installment of the Prepare for College Biology series. We have covered homeostasis, general chemistry and organic chemistry. This week’s topic is cell membranes.
Basic Structure of the Cell Membrane
The cell has a membrane around it. The membrane is primarily made up of a fat called phospholipids. This is an example of fats being used for structure in an organism. These phospholipids create a bi-layer. Each orients with the phosphate to the inside or outside of the cell (where there is a lot of water) and the fatty acids are oriented towards each other.
Function of the Cell Membrane
The main job of the cell membrane is to be the boundary of the cell and control what goes into and out of the cell and by doing that it maintains homeostasis.
The key factors that impact whether a substance move across the membrane are:
- Does it dissolve in fats?
- Does it have a charge?
- How big is it?
- Is there something in place to carry it across the membrane?
The cell membrane can also play a role in receptor function and contact between cells.
Use that Background Knowledge
Hopefully you are activating your general chemistry skills! Remember how most organisms are mostly water? Water and fat repel each other (think of the sink full of water and grease – gross but the image sticks). What that means is that most things in the body don’t dissolve well in fats (nonpolar). That isn’t the only factor, but it is the primary reason that cells have so many transport and channel proteins in the cell membranes. It is important that substances move across so these proteins provide a path, when the other factors make it less likely to occur.
Don’t Forget Homeostasis.
Once there is a path, there is another factor that impacts how much of a substance moves across. That factor is how much there is of the substance. If there is 5 parts of substance A inside the cell and 5 parts outside the cell, there is no push for substance A to move. It has reached equilibrium. All systems naturally tend toward equilibrium. That means that substance A isn’t going to move without some help in the form of energy. If substance B has 6 parts inside the cell and 12 parts outside the cell, substance B will move into the cell naturally following equilibrium. It will move until there are 9 parts in and 9 parts out (as long as there is a way to move between the cells).
If you have enjoyed this post. You can get more details about cellular membranes including information about passive and active transport and tonicity by clicking here.
Let other people know.
If you are finding this series helpful, please tweet it out so that other people can get the same benefit!
Tweet: Check out this refresher on biology concepts from The Learning Hypothesis! http://bit.ly/2a2BlYe #biologyreview #collegeprep #readyforfall
