Biomembrane Structure

Study Notes

All cells have a membrane that is essential for their function.
Prokaryotic cells have a single plasma membrane, while eukaryotic cells have many membrane-covered cell organelles.
The membrane is made of phospholipids that spontaneously form bilayers.
Each lipid layer is called a leaflet.
The bilayer is embedded with many types of proteins.
The membrane is selectively-permeable and provides stability to the cell.
The cell maintains tonicity by regulating the levels of water inside and outside of the cell.
Membrane lipids are amphipathic and are composed of two segments with very different chemical properties.
Phosphoglycerides have various head group attachments to the phosphate group, while sphingolipids have a single fatty acid attached by an ether linkage.
Fatty acids of phospholipids are long chains of hydrocarbons with various degrees of saturation.
Plasmalogens have one fatty acid attached by an ether linkage and one by an ester linkage.
Membranes are conserved across different cells and are composed of phospholipids, proteins, and lipid bilayers.
Membrane lipids play an important role in determining the physical properties of membranes.
Membrane fluidity decreases with the presence of sphingolipids and cholesterol, while it increases with the presence of phosphoglycerides.
Membrane lipid distribution is asymmetrical between exoplasmic and cytoplasmic leaflets, with cholesterol being fairly evenly distributed.
Membrane proteins interact with membranes in three ways: transmembrane proteins pass through the membrane once, multipass membrane proteins pass through the membrane multiple times, and glycoproteins and glycolipids are only found in the exoplasmic face of the plasma membrane.