Welcome to My AP Biology Thoughts podcast, my name is Nikki Evich and I am your host for episode #52 called Unit 2 Cell Structure and Function: Macromolecules that make up the Cell Membrane. Today we will be discussing the structure of the cell membrane.
Segment 1: Introduction to the fluid mosaic model
So what is a fluid mosaic model?
A fluid mosaic model describes the structure of the plasma membrane as a mosaic of components that gives the membrane a fluid character
fluid combination of phospholipids, cholesterol, and proteins.
All in all- made up of a bunch of different molecules that are distributed across the membrane. If you were to zoom in on the cell membrane, you would see a pattern of different types of molecules put together, also known as a mosaic. These molecules are constantly moving in two dimensions, in a fluid fashion, similar to icebergs floating in the ocean.
Segment 2: More About each macromolecule
Phospholipid bilayer- made of of hydrophobic tails and hydrophilic heads
Saturated fatty acids are chains of carbon atoms that have only single bonds between them. As a result, the chains are straight and easy to pack tightly. Unsaturated fats are chains of carbon atoms that have double bonds between some of the carbons. The double bonds create kinks in the chains, making it harder for the chains to pack tightly
Double or triple bonds- not organized
Saturated better organized
Cholesterol-help with structure and fluidity of the because they prevent the phospholipid bilayer from separating too far
The cholesterol molecules are randomly distributed across the phospholipid bilayer, helping the bilayer stay fluid in different environmental conditions.
Without cholesterol, the phospholipids in your cells will start to get closer together when exposed to cold, making it more difficult for small molecules, like gases to squeeze in between the phospholipids like they normally do. Without cholesterol, the phospholipids start to separate from each other, leaving large gaps.
Glycolipid- lipid with a carb attached outside of cell membranes
Help stabilize membrane structure
Glycoprotein-protein with a carb attached
Help stabilize membrane structure
Many different proteins
acts like a pore in the membrane that lets water molecules or small ions through quickly ○ Peripheral proteins (hang on side)
transport or communication
Integral protein (all the way through)
transporting larger molecules, like glucose, across the cell membrane. They have regions, called “polar” and “nonpolar” regions, that correspond with the polarity of the phospholipid bilayer
What affects cell fluidity besides
Temperature-high lipids spread, low they get too close
Segment 3: Connection to the Course
Why is the cell membrane so important?
Fluid form makes it not totally closed off but
permeable-permeability is very important so the cell can import and export
Plays a role in homeostasis
Allows cell to survive in diverse environments
We learned about all the different macromolecules and how
they make up cells- this is an example of how macromolecules make up an
integral part of the cell
Thank you for listening to this episode of My AP Biology Thoughts. For more student-ran podcasts and digital content, make sure that you visit www.hvspn.com. See you next time!
“Ice Flow” Kevin MacLeod (incompetech.com)
Licensed under Creative Commons: By Attribution 4.0 License