cell membrane

Examples of cell membrane in the following topics:

• Electric Potential in Human

  • Electric potentials are commonly found in the body, across cell membranes and in the firing of neurons.
  • In humans, they are seen in cell membranes and nerve impulses in particular.
  • Resting membrane potential is approximately -95 mV in skeletal muscle cells, -60 mV in smooth muscle cells, -80 to -90 mV in astroglia, and -60 to -70 mV in neurons.
  • Potentials can change as ions move across the cell membrane.
  • Active transport of ions across a cell membrane is also a possibility.

• Injuring the Plasma Membrane

  • The plasma membrane or cell membrane is a biological membrane that separates the interior of all cells from the outside environment.
  • The membrane basically protects the cell from outside forces.
  • Plasma membranes are involved in a variety of cellular processes such as cell adhesion, ion conductivity, and cell signaling.
  • They disrupt the structure of the bacterial cell membrane by interacting with its phospholipids.
  • Diagram of a typical gram-negative bacterium, with the thin cell wall sandwiched between the red outer membrane and the thin green plasma membrane.

• Exocytosis

  • In exocytosis, waste material is enveloped in a membrane and fuses with the interior of the plasma membrane.
  • This fusion opens the membranous envelope on the exterior of the cell and the waste material is expelled into the extracellular space .
  • The next stage that occurs is vesicle tethering, which links the vesicle to the cell membrane by biological material at half the diameter of a vesicle.
  • Next, the vesicle's membrane and the cell membrane connect and are held together in the vesicle docking step.
  • Some examples of cells using exocytosis include: the secretion of proteins like enzymes, peptide hormones and antibodies from different cells, the flipping of the plasma membrane, the placement of integral membrane proteins(IMPs) or proteins that are attached biologically to the cell, and the recycling of plasma membrane bound receptors(molecules on the cell membrane that intercept signals).

• Components of Plasma Membranes

  • The plasma membrane (also known as the cell membrane or cytoplasmic membrane) is a biological membrane that separates the interior of a cell from its outside environment.
  • The primary function of the plasma membrane is to protect the cell from its surroundings.
  • Plasma membranes must be very flexible in order to allow certain cells, such as red blood cells and white blood cells, to change shape as they pass through narrow capillaries.
  • The membrane also maintains the cell potential.
  • The cell employs a number of transport mechanisms that involve biological membranes:

• The Plasma Membrane and the Cytoplasm

  • Despite differences in structure and function, all living cells in multicellular organisms have a surrounding plasma membrane (also known as the cell membrane).
  • Wastes (such as carbon dioxide and ammonia) also leave the cell by passing through the membrane.
  • Another form of this type of transport is endocytosis, where a cell envelopes extracellular materials using its cell membrane.
  • The cell's plasma membrane also helps contain the cell's cytoplasm, which provides a gel-like environment for the cell's organelles.
  • Explain the structure and purpose of the plasma membrane of a cell

• Fluid Mosaic Model

  • For comparison, human red blood cells, visible via light microscopy, are approximately 8 µm wide, or approximately 1,000 times wider than a plasma membrane.
  • The proportions of proteins, lipids, and carbohydrates in the plasma membrane vary with cell type.
  • Thus, the membrane surfaces that face the interior and exterior of the cell are hydrophilic.
  • In contrast, the middle of the cell membrane is hydrophobic and will not interact with water.
  • Therefore, phospholipids form an excellent lipid bilayer cell membrane that separates fluid within the cell from the fluid outside of the cell.

• Gram-Negative Outer Membrane

  • The Gram-negative cell wall is composed of an outer membrane, a peptidoglygan layer, and a periplasm.
  • In the Gram-negative Bacteria the cell wall is composed of a single layer of peptidoglycan surrounded by a membranous structure called the outer membrane.
  • It contains structures that help bacteria adhere to animal cells and cause disease.
  • Sandwiched between the outer membrane and the plasma membrane, a concentrated gel-like matrix (the periplasm) is found in the periplasmic space.
  • Together, the plasma membrane and the cell wall (outer membrane, peptidoglycan layer, and periplasm) constitute the gram-negative envelope.

• Membrane Potentials as Signals

  • The membrane potential allows a cell to function as a battery, providing electrical power to activities within the cell and between cells.
  • Membrane potential (also transmembrane potential or membrane voltage) is the difference in electrical potential between the interior and the exterior of a biological cell.
  • All animal cells are surrounded by a plasma membrane composed of a lipid bilayer with a variety of types of proteins embedded in it.
  • First, it allows a cell to function as a battery, providing power to operate a variety of "molecular devices" embedded in the membrane.
  • In non-excitable cells, and in excitable cells in their baseline states, the membrane potential is held at a relatively stable value, called the resting potential.

• Characteristics of Eukaryotic Cells

  • A eukaryotic cell has a true membrane-bound nucleus and has other membranous organelles that allow for compartmentalization of functions.
  • Like a prokaryotic cell, a eukaryotic cell has a plasma membrane, cytoplasm, and ribosomes.
  • However, unlike prokaryotic cells, eukaryotic cells have:
  • Eukaryotic cells have a true nucleus, which means the cell's DNA is surrounded by a membrane.
  • Other than the fact that vacuoles are somewhat larger than vesicles, there is a very subtle distinction between them: the membranes of vesicles can fuse with either the plasma membrane or other membrane systems within the cell.

• Dendritic Cells

  • Dendritic cells are immune cells that function to process antigens and present them to T cells.
  • These cells are identified morphologically by their membranous projections that resemble spines .
  • Mature dendritic cells reside in the T cell zones of the lymph nodes, and in this location they display antigens to T cells.
  • This communication can take the form of direct cell-to-cell contact based on the interaction of cell-surface proteins.
  • An example of this includes the interaction of the membrane proteins of the B7 family of the dendritic cell with a CD28 cell surface molecule present on the lymphocyte.