Summary
Describes the membrane as a flexible fluid bilayer in which proteins float and move laterally like a mosaic.
In depth
Proposed by Singer and Nicolson in 1972, the model describes proteins floating in a fluid lipid sea. Lipids and many proteins drift laterally within the layer, but flipping between layers is rare. Carbohydrate chains on the outer surface form the glycocalyx.
The membrane is asymmetric, with different lipids and proteins on each side. Proteins may be restricted by the cytoskeleton or by lipid rafts, so the membrane is a patchwork not a uniform liquid.
Evidence: the mixing of labelled mouse and human cell surface proteins after cell fusion showed lateral movement.
Integral proteins span the bilayer with alpha-helical segments of hydrophobic amino acids, while peripheral proteins attach to the surface. Not all proteins drift freely: some are held by the cytoskeleton or confined in lipid rafts, small cholesterol-rich domains that gather signalling molecules.
Experiments supporting fluidity include fusing mouse and human cells and watching their surface proteins intermix within about 40 minutes, and FRAP, in which a bleached patch of fluorescent molecules recovers as neighbours move in.
Remember: the sugar chains of glycoproteins and glycolipids face outward only; this asymmetry is set up in the ER and Golgi lumen and preserved when vesicles fuse with the plasma membrane.
Frequently asked questions
What is Fluid Mosaic Model?
Describes the membrane as a flexible fluid bilayer in which proteins float and move laterally like a mosaic.
Which area of biology covers Fluid Mosaic Model, and how advanced is it?
Fluid Mosaic Model is one of the 52 topics in Cell Biology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Plasma Membrane, Phospholipid Bilayer, Exocytosis.
What should I learn before Fluid Mosaic Model?
Work through the Beginner topics in Cell Biology first, such as Cell Theory, Prokaryotic Cell, Eukaryotic Cell, then return to Fluid Mosaic Model. Intermediate topics assume the Beginner vocabulary.
What topics are related to Fluid Mosaic Model?
The closest topics to Fluid Mosaic Model are Plasma Membrane, Phospholipid Bilayer, Exocytosis, Golgi Apparatus. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Fluid Mosaic Model?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Fluid Mosaic Model. To practise the whole of Cell Biology, use the Cell Biology quiz.
How is Fluid Mosaic Model different from Plasma Membrane?
Fluid Mosaic Model: Describes the membrane as a flexible fluid bilayer in which proteins float and move laterally like a mosaic. Plasma Membrane: The thin, selectively permeable phospholipid boundary that separates the inside of a cell from its surroundings. Read both side by side and note what each one explains.
How should I study Fluid Mosaic Model step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Plasma Membrane and explain the difference aloud. Finally, take the Cell Biology quiz and come back to this page for any question you miss.