permeable

Examples of permeable in the following topics:

• Chemiosmosis and Oxidative Phosphorylation

  • Chemiosmosis is the movement of ions across a selectively permeable membrane, down their electrochemical gradient.
  • The electrons cause conformation changes in the shapes of the proteins to pump H+ across a selectively permeable cell membrane.  

• Selective Permeability

  • Describe how membrane permeability, concentration gradient, and molecular properties affect biological diffusion rates.

• Introduction to Osmoregulation

  • Osmoregulation balances concentrations of solutes and water across semi-permeable membranes, maintaining homeostasis.
  • The membranes of the body (such as the pleural, serous, and cell membranes) are semi-permeable: they allow passage of certain types of solutes and water, but not others.
  • Solutions on two sides of a semi-permeable membrane tend to equalize in solute concentration by movement of solutes and/or water across the membrane.
  • Isotonic cells have an equal concentration of solutes inside and outside the cell; this equalizes the osmotic pressure on either side of the semi-permeable membrane.

• The Plasma Membrane and the Cytoplasm

  • The membrane's lipid bilayer structure provides the cell with access control through permeability.
  • This structure causes the membrane to be selectively permeable.
  • A membrane that has selective permeability allows only substances meeting certain criteria to pass through it unaided.
  • Osmosis is the diffusion of water through a semi-permeable membrane down its concentration gradient.
  • If a membrane is permeable to water, though not to a solute, water will equalize its own concentration by diffusing to the side of lower water concentration (and thus the side of higher solute concentration).

• Osmosis

  • Semipermeable membranes, also termed selectively permeable membranes or partially permeable membranes, allow certain molecules or ions to pass through by diffusion.
  • In the diagram shown, the solute cannot pass through the selectively permeable membrane, but the water can.

• Transport of Electrolytes across Cell Membranes

  • Water passes through semi-permeable membranes by passive diffusion, moving along a concentration gradient and equalizing the concentration on either side of the membrane.
  • Electrolyte ions may not be able to passively diffuse across a membrane, but may instead require special mechanisms to cross the semi-permeable membrane.

• Components of Plasma Membranes

  • Composed of a phospholipid bilayer with embedded proteins, the plasma membrane is selectively permeable to ions and organic molecules and regulates the movement of substances in and out of cells.
  • The movement of a substance across the selectively permeable plasma membrane can be either "passive"—i.e., occurring without the input of cellular energy—or "active"—i.e., its transport requires the cell to expend energy.

• Hormonal Control of Blood Calcium Levels

  • If calcium levels get too high, membrane permeability to sodium decreases and membranes become less responsive.
  • If calcium levels get too low, membrane permeability to sodium increases and convulsions or muscle spasms may result.

• The Role of Passive Transport

  • In other words, plasma membranes are selectively permeable; they allow some substances to pass through, but not others.
  • Diffusion through a permeable membrane moves a substance from an area of high concentration (extracellular fluid, in this case) down its concentration gradient (into the cytoplasm).

• Kidney Function and Physiology

  • In the loop of Henle, the permeability of the membrane changes.
  • The descending limb is permeable to water, not solutes; the opposite is true for the ascending limb.
  • The descending limb is water permeable.