015 - Cell Membranes — bozemanscience

Paul Andersen explains how cells are selectively permeable with the help of their cell membrane

History of cell membrane theory - Wikipedia

Eukaryotes also have membrane lipid innovations that are not found in either Archaea or Bacteria: and . Sterols (like cholesterol) and sphingolipids (phospholipids with fatty acid chains linked to the amino acid serine instead of to glycerol) are major components of eukaryotic plasma membranes, and together can constitute 50% of the lipids of the outer leaflet (Desmond and Gribaldo, 2009; sphingolipids are not found in the cytoplasmic side of the plasma membrane lipid bilayer). Sterols are essential in all eukaryotic cell membranes. Sterols reduce membrane fluidity and permeability, and increase membrane rigidity and strength. Together with sphingolipids they help organize regions of the membrane into , microdomains in the plasma membrane with increased rigidity, that organize cell signaling proteins into functional complexes (see review by Lingwood and Simons, 2010).

In apoptosis, the cell membrane does not rupture, the cell contents are not released into the extracellular space, and inflammation does not occur.

Investigating Factors that Affect Cell Membrane Permeability

Certain clostridia, for example, produce phospholipase enzymes that break down cell membranes and enable the bacteria to flourish briefly in dead tissue.

Obviously, cell systems for maintaining membranes, metabolism, enzyme synthesis, and gene preservation are inter-linked, and whatever affects one will affect the other.


How do cells transport molecules like glucose across the membrane? Membranes have dedicated transport proteins with transmembrane domains. Several transmembrane domains cluster to form channels in the membrane that are specific for various molecules like glucose, phosphate, Na+, H+, Cl-, and even H2O. Water transport is mediated by highly conserved proteins called aquaporins, which are present in all 3 domains of life.

Caco-2 cell permeability assays to measure drug …

Cells are adapted to their aqueous environment in terms of their cytoplasmic solute concentrations. Mammalian cells have cytoplasmic solute concentrations that balance the physiological salt concentrations. In physiological saline solutions, mammalian cells are in an isotonic environment, meaning the solute concentrations inside the cell and outside the cell are in balance, so there is no net movement of water across the cell membrane. In a hypotonic solution, the solute concentration outside the cell is lower than inside the cell, so water will enter the cell to try to reduce the internal solute concentration. In a hypertonic solution, the solute concentration outside is higher than inside the cell, so water will exit the cell and the cell will shrivel up.

The Microbiome Activates CD4 T-cell–mediated …

Microvilli (if any) flatten, blebs form on the cell surface, and the membranes of disrupted organelles form laminated figures ("myelin-like", alternatinglayers of water and lipid formed from phosphlipid) in the injured cytoplasm.