Question

This is a Physiology qquestion. Describe the two general meanings of the term membrane, as used in biology. Which usage indicates layers of cells and which indicates layers of molecules?

Answer 1

Answer:

Two general meanings of the term "membrane" in biology are to describe the structure of cell membrane that is permeable to some molecules but not all molecules. Second meaning of a "membrane in biological cell" is to protect inner cytoskeleton with organelles. Membrane is made of phospholipid bilayer in which one is hydrophilic region and another is hydrophobic region. The phsopholipid layers indicates layers of lipids and membrane proteins whereas the layers of cells is mainly due to "membrane associated cell adhesion molecules"

These three macromolecules together to form a complex phospholipid bilayer in which periplasmic proteins are distributed in a mosaic manner. The large fluid mosaic structure is formed from these macromolecules composed of phospholipid bilayers with protein channels for the transport of organic & inorganic nutrients including trace metal. Normally, the essential aspects of these structures composed of "porins, protein channels, integral proteins” that dictate their function for the selective permeability, diffusion of nutrients across the membrane into & out of the cell finally to attain homeostasis

Fluid mosaic model describes that two-dimensional liquid layer of cell membrane where proteins distributed like mosaic model in the phospholipid bilayer. This model mostly accepted by biologists Role of the protein molecules in this model cell membrane layers are membrane extracellular protein domains in connection to the lipid bilayer membrane. Membrane phospholipids are the molecules with hydrophillic polar heads towards the solvent such as water whereas hydrophobic tail located towards the center of the layer and this bilayer formed by micelles, as fatty acids possess one polar associated with another nonpolar head. Cell membrane possesses a property known as selective permeability. Cell membrane consists of phopholipid bilayer that also include several of the transmembrane proteins, ion channels etc. Small, non-polar molecules with hydrophobic nature diffuse more easily into the cell membrane. Similarly, proteins interact and assemble themselves to form several layers of structures in our body.