Biology

Cellular Transport Notes

Cytology is the study of cells.

Cytoplasm is the jelly-like clear fluid in cells

 

Cellular Transport – movement of materials into and out of the cell

                                          selectively permeable  cell membrane allows transport to occur

Two types of Cellular Transport

1. Active Transport
   1. requires energy (energy in the cell is ATP)
   2. moves from an area of lesser concentration to an area of greater

concentration

concentration gradient – change in concentration over a given area

Examples of Active Transport

a.       endocytosis – the process by which a substance that cannot pass through

                             the cell membrane enters the cell

                            Two types of endocytosis:

1.      phagocytosis – a cell engulfs large particles or whole cells in

                               cytoplasm

 

2.      pinocytosis – the cell engulfs large droplets or solutes of fluids

 

 

 

 

 

 

 

 

 

b.      exocytosis – the process in which a vesicle inside a cell fuses with a cell

                           membrane and releases its contents to the external

                           environment

a.       substance that cannot pass through the cell membrane

      exits the cell

             Steps of Exocytosis

1.      vesicle forms around the material that needs to leave the cell

2.      vesicle moves toward the cell membrane

3.      vesicle membrane fuses with the cell membrane

4.      cell membrane breaks releasing the contents of the vesicle, but maintaining the integrity of the cell

 

2.Passive Transport

                        a.  does not require energy (does not require ATP the energy for the cell)

b.  moves from an area of greater concentration to an area of lesser

     concentration

      c.  substances move down the concentration gradient

 

                        Examples of Passive Transport

a.       diffusion – the process by which molecules move from an area of

                         greater concentration to an area of lesser concentration

b.      osmosis – the diffusion of water across a selectively permeable

                       membrane

1.      osmosis is controlled by the type of solution

Types of solutions

1.      hypertonic solution – water is more concentrated inside the cell

                                          than outside the cell

a.       water moves (diffuses) out of the cell

b.      plasmolysis occurs – cell shrinks due to water loss

c.       plasmolysis causes wilting in plants due to a loss of

      turgor pressure – turgor pressure is water pressure that

      gives the plant support when water fills the large central

      vacuole

2.      hypotonic solution – water is more concentrated outside

                                        the cell than inside the cell

a.       water moves (diffuses) into the cell

b.      cytolysis occurs – cell bursts due to excess water

c.       contractile vacuoles pump out excess water and prevent cytolysis in freshwater unicellular organisms

d.      cell walls prevent cytolysis in plant cells

e.       hypotonic solutions create turgor pressure in plant cells

3.      isotonic solution – water is equally concentrated inside and

                                    outside the cell

a.       there is no net movement of water

 

 

 

 

cytolysis

plasmolysis

                                                                              turgor pressure

 

 

 

c.       facilitated diffusion – diffusion aided by carrier molecules

1.      carrier molecules are the proteins in the cell membrane

 

 

 

d.      gated channels – proteins that allow the passage of molecules (ions)

                                   that cannot pass through the phospholipid bilayer.

 

 

 

Compare and Contrast Active and Passive Transport

Compare:

1. both are types of transport

2. both move substances into and out of the cell

3. both are necessary for the cell to survive

Contrast:

1. active transport requires energy; passive transport does not require energy

2. active transport moves up or against the concentration gradient; passive transport

    moves down the concentration gradient

3. active transport moves from an area of lesser concentration to greater concentration;

    passive transport moves from an area of greater concentration to an area of lesser

    concentration