transport across membranes

• phospholipids (vocab)


  two layers of lipid molecules in the cell membrane which can have protein molecules imbedded
• proteins (vocab)


  structures that make up part of the cell membrane and are embedded in the phospholipid bilayer
• selectively permeable (vocab)

  refers to a membrane that controls the movement of certain molecules depending on their size
• passive (vocab)


  the movement of molecules without the need for additional energy (ex. diffusion & osmosis)
• diffusion (vocab)


  the passive movement of molecules from an area of higher concentration to an area of lower concentration
• osmosis (vocab)


  movement of water molecules from an area of higher water concentration to an area of lower water concentration through selectively permeable membrane
• burst (vocab)


  when an animal cell gains water by osmosis
• shrink (vocab)


  when an animal cell loses water by osmosis
• turgid (vocab)


  a swollen plant cell with a full vacuole resulting from water intake due to osmosis
• plasmolysed (vocab)


  a plant cell in which the vacuole has shrunk and the membrane has pulled away from the wall due to water loss
• active (vocab)


  the transport of molecules against their concentration gradient that requires energy
• cell membrane (vocab)


  controlling the entry and exit of materials within a cell
• concentration gradient (vocab)


  a difference in concentration between two solutions, cells or solutions and cells
• a living cell needs to take in oxygen and get rid of carbon dioxide
• usually, only particles that are small and soluble can pass through the plasma membrane as they can dissolve more easily than larger ones do
• glucose is soluble in water
• concentration gradient

  since the cell membrane is selectively permeable, this means some substances can pass across whilst others cannot. this can create differences in concentrations of substances on one side of the membrane compared to another.
• the movement down a concentration gradient

  substances move from an area of high concentration to a low concentration
• the movement against a concentration gradient

  substances move from an area of low concentration to a high concentration
• examples of passive transport:

  diffusion

  osmosis
• how quickly do these particles move (fastest to slowest)

  1. gases
  2. liquids
  3. solids
• diffusion 


  a very important process in cells as it is how they gain useful substances and get rid of waste substances.
• osmosis 


  the movement of water molecules from a higher to a lower water concentration through a selectively permeable membrane
• state two features that plant cells have but animal cells do not have

  cell wall - provides shape and support to the cell

  vacuole - stores cell sap
• can plant cells reverse the effects of osmosis?

  yes as they have a cell wall and vacuole
• the effects of osmosis on plant cells

  
• the effect of osmosis on animal cells

  
• active transport

  • movement from a lower to higher concentration
  • molecules move against the concentration gradient
  • protein pumps are involved
  • requires energy
• passive transport

  • movement from a higher to lower concentration
  • molecules move down the concentration gradient
  • protein pores are involved
  • does not require energy
• how protein pumps within membranes change shape to move molecules and ions from one side to another: