Cell Membrane

  1. Plasma Membrane (Cell Membrane)

    • The semi-permeable barrier that surrounds the cell, made of a phospholipid bilayer with embedded proteins. It controls the movement of substances in and out of the cell.

  2. Phospholipid Bilayer

    • A double-layered membrane structure where hydrophilic (water-attracting) heads face outward toward the aqueous environment, and hydrophobic (water-repelling) tails face inward, away from water.

  3. Integral Proteins

    • Proteins that span across the membrane, often functioning as channels or carriers for molecules to pass through the membrane.

  4. Peripheral Proteins

    • Proteins that are attached to the exterior or interior surface of the membrane, involved in cell signaling or maintaining the cell's shape.

  5. Fluid Mosaic Model

    • Describes the structure of the plasma membrane as a dynamic, flexible arrangement of components (lipids and proteins) that can move within the layer.

  6. Selective Permeability

    • The property of the plasma membrane that allows only certain molecules to pass through while blocking others.

  7. Passive Transport

    • The movement of substances across the membrane without the need for energy. Includes processes like diffusion and osmosis.

  8. Active Transport

    • The movement of substances across the membrane against their concentration gradient, requiring energy (typically in the form of ATP). Examples include pumps like the sodium-potassium pump.

  9. Diffusion

    • The movement of molecules from an area of higher concentration to an area of lower concentration, driven by the concentration gradient.

  10. Facilitated Diffusion

    • A form of passive transport where molecules move across the membrane with the help of a protein channel or carrier, typically for larger or polar molecules (e.g., glucose, ions).

  11. Osmosis

    • The diffusion of water molecules across a semi-permeable membrane from an area of lower solute concentration to an area of higher solute concentration.

  12. Concentration Gradient

    • The difference in concentration of a substance between two areas. Molecules tend to move from high to low concentration.

  13. Endocytosis

    • The process by which a cell engulfs external substances, forming vesicles that bring the substances into the cell. Types include phagocytosis (solid material) and pinocytosis (liquid material).

  14. Exocytosis

    • The process by which a cell expels substances using vesicles that fuse with the plasma membrane, releasing the contents outside the cell.

  15. Ion Channels

    • Protein channels that allow ions (charged particles) to pass through the membrane. These channels can be specific to certain ions like Na+, K+, or Ca2+.

  16. Sodium-Potassium Pump

    • A type of active transport pump that moves sodium (Na+) out of the cell and potassium (K+) into the cell, against their concentration gradients, using ATP.

  17. Endoplasmic Reticulum (ER)

    • A network of membranes involved in protein and lipid synthesis. The rough ER has ribosomes attached to it, while the smooth ER does not.

  18. Golgi Apparatus

    • An organelle involved in modifying, sorting, and packaging proteins and lipids for transport or secretion from the cell.

  19. Vesicles

    • Small membrane-bound sacs that transport materials within and outside the cell.