Proteins stop fish from freezing

Fish in the Antarctic live in salt water that can be below normal freezing point. If the water inside the fish froze then its volume would increase and the fishes’ cells would burst, so they protect themselves from the cold with special glycopeptides – amino acid strings in which a threonine side chain has a sugar molecule attached. Any ice crystals that form become coated with this natural antifreeze and remain too small to cause damage.

Such natural antifreeze molecules could help to improve tissue preservation in medicine (eg in sperm banks or when donated organs have to be shipped for transplant in another hospital). They could even be applied in cryonics, where people pay to have their bodies – or sometimes just their heads – frozen after death, in the hope that one day medicine will be sufficiently advanced to bring them back to life.

Questions for discussion

  • Would you want your body to be frozen after you die? Why?
  • What would be the consequences if this practice became routine?
  • How are doctors using low temperatures? (Hint: Start exploring this by searching for ‘therapeutic hypothermia’ online.)

About this resource

This resource was first published in ‘Proteins’ in January 2014.

Cell biology, Medicine, Biotechnology and engineering
Education levels:
16–19, Continuing professional development