Cell Membrane Fusion and Fluid Mosaic Model Quiz

Study Notes

The fluid mosaic model of membrane structure states that phospholipid bilayer of a membrane contains proteins inserted in it or associated with its surface, and these proteins move within the fluid lipid phase.
Integral proteins are firmly embedded in the lipid layers, and those that completely span the bilayer are called transmembrane proteins. Hydrophobic amino acids of these proteins interact with the hydrophobic fatty acid portions of the membrane lipids.
Selective permeability is a property of cell membranes that regulates entry and exit of ions, nutrients, and waste molecules through the membrane. Membrane proteins serve as receptors for various signals coming from outside cells and as selective gateways for molecules entering the cell.
Membrane proteins, such as those for low-density lipoproteins and protein hormones, act as receptors at the cell surface. High-affinity binding of these ligands to their receptors causes aggregation of these proteins in special membrane regions, leading to invagination and pinching off internally as vesicles.
Cells open and close specific channels for ions (such as sodium) across the membrane. Membrane components, including proteins and lipids, have externally exposed oligosaccharide chains that contribute to the cell's glycocalyx.
Electron microscopy is a useful method for studying membrane structures by examining cryofracture preparation replicas. Most of the protruding membrane particles seen are proteins or aggregates of proteins attached to the half of the membrane adjacent to the cytoplasm, and fewer particles are found attached to the outer half.
Vesicular transport, specifically endocytosis and exocytosis, is a process by which macromolecules enter cells by being enclosed within folds of the plasma membrane. Three major types of endocytosis are recognized: phagocytosis (ingestion of particles), pinocytosis (bulk fluid uptake), and receptor-mediated endocytosis (specific molecule uptake).
The plasma membrane maintains an electrical charge difference across it through electrochemical gradients. Communication between cells occurs through receptors and connections.