Biology 11th Edition by Cecie Starr ,Ralph Taggart

تمرين 5

ATP forms in mitochondria. In warm-blooded animals, so does a lot of heat, which is circulated in ways that help control body temperature. Cells of brown adipose tissue make a protein that disrupts the formation of electron transfer chains in mitochondrial membranes. H + gradients are affected, so fewer ATP form; electrons in the transfer chains give up more of their energy as heat. Because of this, some researchers hypothesize that brown adipose tissue may not be like white adipose tissue, which is an energy (fat) reservoir. Brown adipose tissue may function in thermogenesis, or heat production.
Mitochondria, recall, contain their own DNA, which may have mutated independently in human populations that evolved in the Arctic and in the hot tropics. If that is so, then mitochondrial function may be adapted to climate.
How do you suppose such a mitochondrial adaptation might affect people living where the temperature range no longer correlates with their ancestral heritage Would you expect people whose ancestors evolved in the Arctic to be more or less likely to put on a lot of weight than those whose ancestors lived in the tropics See Science , January 9, 2004: 223226 for more information.