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Macromolecules that Make up the Cell Membrane
Episode 524th May 2021 • My AP Biology Thoughts • Hopewell Valley Student Publications Network
00:00:00 00:07:25

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My AP Biology Thoughts 

Unit 2 Cell Structure and Function 

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. 
  • Carbons 
  • Glycolipid- lipid with a carb attached outside of cell membranes 
  • Help stabilize membrane structure 
  • Glycoprotein-protein with a carb attached 
  • Help stabilize membrane structure 
  • Proteins 
  • Many different proteins 
  • Channel 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
  • needed materials 
  • 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 See you next time!

Music Credits:

  • “Ice Flow” Kevin MacLeod (
  • Licensed under Creative Commons: By Attribution 4.0 License

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