Plasma Membrane and Membrane Proteins PDF

Plasma Membrane Cell Biology and Membrane Proteins Lokender Kumar Ph.D. Cell biology Lokender Kumar Ph.D. Cell biology Lokender Kumar Ph.D. Fluid Mosaic Model The fluid mosaic model was first...

Plasma Membrane Cell Biology and Membrane Proteins Lokender Kumar Ph.D. Cell biology Lokender Kumar Ph.D. Cell biology Lokender Kumar Ph.D. Fluid Mosaic Model The fluid mosaic model was first proposed by S.J. Singer and Garth L. Nicolson in 1972 to explain the structure of the plasma membrane. Credit: https://bio.libretexts.org/ Cell biology Lokender Kumar Ph.D.  Plasma Membrane Biological membrane Separates the interior Protects the cell from its environment lipid bilayer, Phospholipids with cholesterols (a lipid component) Maintaining appropriate membrane fluidity at Plasma membrane various temperatures. Credit: https://en.wikipedia.org/wiki/Cell_membrane Cell biology Lokender Kumar Ph.D.  Plasma Membrane Cell adhesion, Ion conductivity Cell signaling and Attachment surface for several extracellular structures Cell membranes can be artificially reassembled. Cell biology Lokender Kumar Ph.D. Credit: https://en.wikipedia.org/wiki/Cell_membrane Cell biology Lokender Kumar Ph.D.  Lipids This phospholipid molecule is composed of a → hydrophilic head and two hydrophobic tails. The hydrophilic head group consists of a phosphate-containing group attached to a glycerol molecule. The hydrophobic tails, each containing either a saturated or an unsaturated fatty acid, are long hydrocarbon chains. Credit: https://bio.libretexts.org/ Cell biology Lokender Kumar Ph.D.  Lipids three classes of amphipathic lipids: phospholipids, glycolipids, and sterols. Majority of cases phospholipids are the most abundant, often contributing for over 50% of all lipids Glycolipids only account for a minute amount of about 2% and sterols make up the rest. Cell biology Lokender Kumar Ph.D.  Carbohydrate Plasma membranes also contain carbohydrates, predominantly glycoproteins, but with some glycolipids (cerebrosides and gangliosides). Carbohydrates are important in the role of cell-cell recognition in eukaryotes; they are located on the surface of the cell where they recognize host cells and D-galactose, D-mannose, sialic share information. Viruses that bind to acid, N-acetyl-D-glucosamine, and N-acetyl-D- galactosamine. cells using these receptors cause an infection Cell biology Lokender Kumar Ph.D.  Plasma Membrane Controls the movement of substances in and out of cells Selectively permeable to ions and organic molecules. The membrane also contains membrane proteins Integral proteins membrane transporters, Peripheral proteins that loosely attach to the outer (peripheral) side of the cell membrane Cell biology Lokender Kumar Ph.D. Cell biology Lokender Kumar Ph.D. Cell biology Lokender Kumar Ph.D. Cell biology Lokender Kumar Ph.D.  Proteins Span the membrane and have a hydrophilic cytosolic domain, which Ion channels, Integral proteins interacts with internal molecules, a hydrophobic membrane-spanning proton or domain that anchors it within the cell membrane, and a hydrophilic pumps, G transmembrane extracellular domain that interacts with external molecules. The protein- proteins hydrophobic domain consists of one, multiple, or a combination of α- coupled helices and β sheet protein motifs. receptor Covalently bound to single or multiple lipid molecules; Lipid anchored hydrophobically insert into the cell membrane and anchor the protein. G proteins proteins The protein itself is not in contact with the membrane. Attached to integral membrane proteins or associated with peripheral Some Peripheral regions of the lipid bilayer. These proteins tend to have only enzymes, proteins temporary interactions with biological membranes, and once reacted, some the molecule dissociates to carry on its work in the cytoplasm. hormones Cell biology Lokender Kumar Ph.D.  Exocytosis and Endocytosis Material is incorporated into the membrane, or deleted from it, by a variety of mechanisms: Fusion of intracellular vesicles with the membrane (exocytosis) The membrane may form blebs around extracellular material that pinch off to become vesicles (endocytosis). Cell biology Lokender Kumar Ph.D. Functions Physical barrier between the external environment and the inner cell organelles. Selectively permeable membrane, which permits the movement of only certain molecules both in and out of the cell. Endocytosis and exocytosis process. Communication and signaling between the cells. Anchoring the cytoskeleton to provide shape to the cell and also maintains the cell potential. Cell biology Lokender Kumar Ph.D.