Biological Membranes

• Compartmentalisation


  Separation of the internal contents of the organelle from the substances/chemicals in the cytoplasm
• Fluid mosaic model


  A model that describes membrane structure as a sea of mobile phospholipids studded with various proteins
• Phospholipid


  A type of lipid formed by the condensation of one molecule of glycerol, two molecules of fatty acid and a phosphate group
• Cholesterol


  A mostly hydrophobic molecule that sits in the hydrophobic portion of the membrane and regulates membrane fluidity
• Glycolipid


  Consists of a lipid and a carbohydrate, acts as recognition sides, makes the membrane more stable
• Glycoprotein


  Protein with a sugar molecule attached, acts as recognition sits, maintains stability of membrane
• Carrier Protein


  Facilitates the diffusion of molecules down the concentration gradient, moves molecules against the concentration gradient using active transport
• External/peripheral protein


  A type of protein that is weakly bound to the surface of the membrane
• Integral protein


  A type of protein bound to the membrane with strong interactions
• Simple diffusion


  The spreading out of substances from a high concentration to a lower concentration (down their concentration gradient) without the use of energy
• Facilitated diffusion


  The net movement of substances from a high concentration to a lower concentration (down their concentration gradient) through transport proteins without the use of energy
• Osmosis


  The net movement of water molecules across a partially permeable membrane from a region of high water potential to a region of lower water potential without the use of Energy
• Isotonic solution


  if two solutions have the same water potential they're said to be isotonic
• Amphipathic


  A molecule with both hydrophobic and hydrophilic parts
• Hypotonic solution


  if a cell is placed in a solution that has a high water potential, water will move into the cell by osmosis. Solutions with a higher water potential compared with the inside of the cell are called hypotonic
• Hypertonic


  if a cell is placed in a solution that has a lower water potential, water will move out of the cell by osmosis. Solutions with a lower water potential than the cell are called hypertonic
• Plasmolysis


  The effect produced by placing plant cells in a hypertonic solution causing the cell to shrivel from water loss, resulting in the membrane pulling away from the rigid cell wall
• Crenation


  The shrinking of a cell when placed in a hypertonic solution due to large amounts of water moving out of the cell through osmosis
• Diffusion


  The net movement, as a result of the random motion of its molecules or ions, of a substance from a region of its higher concentration to a region of its lower concentration. The molecules or ions move down a concentration gradient
• Active transport


  the movement of molecules and ions through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration
• Endocytosis


  The bulk uptake of substances into a cell by invagination of the membrane to form a vesicle trapping the substances inside the cell with the use of energy in the form of ATP
• Exocytosis


  The bulk transport of substances out of a cell using a vesicle that fuses with the plasma membrane using energy in the form of ATP
• Hydrophilic


  A molecule which is attracted to water
• Hydrophobic


  A molecule which repels water
• Phagocytosis


  The ingestion of solid material (particularly pathogens and foreign material) by phagocytic cells
• Turgid


  A term used to describe a cell that is swollen due to large amounts of fluid uptake
• Cell lysis


  The bursting of a cell, particularly after the uptake of too much water into an animal cell through osmosis