Name:______________________________

Internet Biology/Cells in the News/Frozen Frogs—Cryosurgery

http://www.pbs.org/wgbh/nova/sciencenow/3209/05.html

 

Log on to the above site and click on “Watch the Segment”.  After watching the segment, click onto “Cold Cures”, and answer the following questions.

 

1)         Explain how chemical damage injures cells during freezing.

When biological materials freeze, the solution found between the cells usually freezes first.  Solutes found in the solution between the cells are ejected from the ice crystals and concentrate in the unfrozen spaces.  This signals the cell to release water outside of the cell because there is a greater concentration of solutes in the unfrozen spaces of the cell than in the cell.  Inside the cell, the loss of water causes an increase in ionic concentration which leads to chemical damage of the cell; thus, it is ions not ice crystals that trigger cell injury during freezing.    

2.         How do the cells of the frog survive freezing?

The cells of the frog survive freezing by producing glucose and incorporating it into the frog’s cell.  This is done by lowering the amount of water that leaves the cell during freezing.  This allows the cell of the frog to survive because the ionic concentration of the cell is reduced and excessive cell shrinkage is avoided.

3.         Define cryoprotectants. 

Cryoprotectants are chemical substances that experts introduce into the cells.  They include glycerol, ethylene glycol, and dimethyl sulfoxide.

4.         What happens to cells in tissue that do not have cryoprotectants?

They do not survive freezing.

5.         Define cryosurgery and the problem it encountered.

Cryosurgery is surgery that uses freezing to destroy cells and tissues.  It was difficult to control the extent of freezing; thus, the probes effect of tissues was not precise.

6.         How did medical imaging help the field of cryosurgery?

Medical imaging allowed the specialist to monitor the extent of freezing inside the body.  Once this happened, the surgeons could freeze the desired shape needed for removing the lesion.  Currently, it is used in the treatment of every type of solid tumor, with tens of thousands of patients being treated with the technique in the US alone.

 

 

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