biology transport of substances

• diffusion


  net movement of particles from an area of higher concentration to an area of lower concentration down their concentration gradient
• partially permeable membrane


  a membrane that allows only certain substances to pass through
• water potential


  concentration of water
• net movement


  the difference in number of molecules moving to and fro either side of the membrane - not represented by a number just whether it is present and the direction
• osmosis


  net movement of water from a solution with a high water potential to a solution with a low water potential, through a partially permeable membrane
• pure water (in terms of water potential)


  highest water potential
• dilute solution (in terms of water potential)

  higher water potential than a dilute solution, lower than a concentrated solution
• concentrated solution (in terms of water potential)


  lowest water potential
• hypertonic


  lower water potential
• hypotonic


  higher water potential
• isotonic


  same water potential
• plasmolysed


  the condition of a plant cell that has lost so much water that its cytoplasm shrinks and pulls the cell membrane away from the cell wall
• flaccid


  the condition of a plant cell where it has lost a bit of water and is less firm
• turgid


  the condition of a plant cell where it has gained water and swollen
• crenated


  a shrivelled animal cell that has lost water by osmosis
• cell lysis


  when an animal cell gains water and bursts by osmosis
• active transport


  movement of molecules into or out of a cell through the cell membrane from a region of low concentration to high concentration against the concentration gradient using energy
• ATP


  adenosine triphosphate, energy released during respiration
• carrier molecule


  in active transport, it picks up specific molecules and takes them through the cell membrane against the concentration gradient - different carriers take different substances
• equillibrium


  a condition in which molecules are spread evenly (equally)
• Passive transport can be further divided into simple diffusion (no carrier proteins involved) or facilitated diffusion (carrier proteins are used).
• Active transport requires energy from ATP to move molecules against their concentration gradients, while passive transport does not require energy as it moves with the concentration gradient.
• The concentration gradient is the difference between the concentrations of a substance on either side of a membrane.