In page 40-41, Dr. Moalem describes how the wood frog reacts to the winter by literally freezing solid during wintertime, with no heartbeat, no breathing and no brain activity; basically dead. According to Big Idea 3, the frog's system reacts to the cold by freezing solid, therefore responding to information essential to its survival. In page 42-43 of the book, Moalem describes how high sugar or glucose content lowers the freezing point in frogs and organisms, allowing the frogs to use the little water in their bloodstream and the high glucose content as antifreeze from the cold.
Why do you think the wood frog differs from all other hibernating mammals in that it literally freezes solid, instead of going into a deep sleep? Why does the wood frog release water from its system and increase sugar levels to deal with the cold? How do you think the wood frog used to live for them to evolve in such a different manner?
Why is sugar and glucose a good antifreeze from the cold? In what disease in humans have we seen that sugar content is high in the body that may help against the cold? How, if possible, can humans use this newfound use of sugar to help our organs revitalize and keep them working?
Rudy Viswanathan (aviswan4@students.d25.org)
There are two chemical reasons for glucose's behavior as a natural antifreeze. Firstly, glucose molecules dissolved in water interfere with the formation of ice crystals. Second, when glucose is incorporated in a cell, as it is in wood frog cells, it helps maintain water content in the cell. We learned that water flows to an area of high solute concentration, so water is more likely to stay in a cell infused with glucose than one without. This water cushion provides physical and chemical protection to the cell: according to an article titled "Cold Cures" on Nova Science Now (Pbs.com) "By lowering the amount of water that leaves the cell during freezing, the glucose offers protection against the rise in ionic concentration and excessive cell shrinkage, thereby reducing chemical harm." In other words, water dilutes harmful ions that can damage the cell.
ReplyDeleteA possible evolutionary advantage to freezing solid is that wood frogs look unappetizing to predators. When frozen, wood frogs are stiff and scentless which acts as a deterrent to predators. Freezing solid helps them survive Therefore, freezing helps a wood frog survive and increases it's chances of reproduction. According to an article titled "Frozen Frogs May Give Docs Jump on Human Transplants," wood frogs lay eggs in ponds created by melted snow -- ponds that do not last very long when summer rolls around. So wood frogs have evolved the ability to thaw with the snow, thus maximizing their opportunity to lay eggs in ponds of melted snow.
Diabetes is the human disease reminiscent of the wood frog. Sugar levels build up in the bloodstream, and some theorize that sugar is acting as an antifreeze in humans, just like it would in wood frogs. Besides theory alone, the study of wood frogs has paved the way for medical advancements. According to the article on Nova Science Now, it was the study of wood frogs that allowed scientists to develop cryopreservation techniques, such as adding glycerol to a cell, that will prevent organic matter from freezing to death. Dr. Boris Rubinsky successfully froze and transplanted a rat liver to a rat that survived for several days. If cryopreservation can be perfected, these techniques may be applied to human transplants, greatly increasing the amount of lives that can be saved.
--Aidan Murphy, amurphy4@students.d125.org