Key words

• Active transport


  The movement of particles across a cell membrane from a region of lower concentration to a region of higher concentration (against the concentration gradient). The process requires energy
• Diffusion


  When particles spread and mix with each other without anything moving them. Diffusion into and out of cells occurs for particles that are small enough to pass throught he cell surface membrane.
• Concentration gradient


  The difference between two concentrations. There will be an overall movement of particles down a concentration gradient, from higher concentration to lower concentration
• Osmosis


  The overall movement of solvent molecules in a solution across a partially permeable membrane, from a dilutes olution to a more concentrated one.
• Passive


  A process that does not require energy is passive. A passive process is the opposite of an active process

  (which requires energy).
• Partially-permiable


  Describes something that will allow certain particles to pass through it but not others.
• Solute


  The solid that has dissolved in a liquid to make a solution.
• Solvent


  The liquid in which a substance dissolves to make a solution.