1.2 biology

• Phospholipids


  Two layers of lipid molecules in the cell membrane which can have protein molecules embedded
• Protein


  Structures that make up part of the cell membrane and are embedded in the phospholipid bilayer
• Selectively permeable


  • A characteristic of the membrane meaning that it controls the movement of certain molecules depending on their size
• Passive transport


  The movement of molecules without the need for additional energy e.g. diffusion and osmosis
• Diffusion


  The passive movement of molecules from an area of high concentration to an area of lower concentration
• Osmosis


  The movement of water molecules from an area of high to an area of lower water concentration through a selectively permeable membrane
• Burst


  When an animal cell gains water by osmosis
• Shrink


  When an animal cell loses water by osmosis
• Turgid


  A swollen plant cell with a full vacuole resulting from water intake due to osmosis
• Plasmolysed


  A plant cell in which the vacuole has shrunk and the membrane has pulled away from the wall due to water loss
• Active transport


  The transport of molecules against their concentration gradient that requires energy
• Cell membrane


  A selectively permeable membrane enclosing the cell cytoplasm and controlling the entry and exit of materials
• Concentration gradient


  A difference in concentration between two solutions, cells or solutions and cells
• A dilute sugar or salt solution will have a higher concentration of water, whereas as concentrated sugar or salt solution will have a lower concentration of water