organisms in hot and cold climates?

[Anonymous1]

Why can't most organisms live in both extremely hot and extremely cold climates?

What reasons do DNA base pairing, protein/enzyme structure, and homeostasis contribute?

Thank you!

[jwalin]

the reason for the protien or enzyme strucure is as follows

the enzymes usually work at an optimum temperature...
they fail to work 100% at any other temperature. and once an organism living in one extreme will have all the enzymes adapted to that temperature and when he suddenly moves to a place that hads the other extreme temperature the organism fails to survive.
humans suurvive in the extremes for we use sweaters.... air conditioners...

once an enzyme doesnt work well all the metabollic process are carried oout at a reduced rate.

[Anonymous1]

Thank you for your help!

Do you know any reason for DNA base pairings?

[JackBean]

temperature optimum is one thing, but IMHO more important is temperature stability, as proteins denature in higher temperatures, so thermophilic organisms must have highly stable enzymes. On the other hand, organisms living in cold must have adapted proteins to this.

Regarding DNA, the difference will probably be in GC%. As GC pair has three H bonds, whereas AT pair has only two, the pairing in GC is more stable and thus thermophilic organisms are more likely to have higher GC content, whereas organisms living in cold will have lower GC%, as it would be too stable to unwind in low temperature.
But that's only my guess, I didn't hear about DNA differences before.

[jwalin]

hmmm
@jackbean
nice thinking *impressive* indeed
could be right