2-18 homeostasis - HOMEOSTASIS LIFE 40.2 40.4 40.2 How does...

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HOMEOSTASIS LIFE 40.2 – 40.4 40.2 How does temperature affect living systems? -If cells cool below 0°C, ice crystals form and damage their structures. Some animals have adaptations , such as antifreeze molecules in their blood, that help them resist freezing; others can survive freezing. Generally, however, cells must remain above 0°C to stay alive -The upper temperature limit for survival in most cells is about 45°C (although some specialized algae can grow in hot springs at 70°C, and some archaea live at near 100°C). In general, proteins begin to denature and lose their function as temperatures rise above 40°C. Therefore, most cellular functions are limited to the range between 0°C and 40°C 40.2.1 Q 10 is a measure of temperature sensitivity -The temperature sensitivity of a reaction or process can be described in terms of Q 10 -If different reactions have different Q 10 values, changes in tissue temperature will shift the rates of some reactions more than others. Thus, a change in tissue temperature can disrupt the balance and integration of the reactions that constitute a physiological process 40.2.2 Animals can acclimatize to a seasonal temperature change - acclimatization : i.e. If the fish can express a number of isozymes that operate at different optimal temperatures, it can catalyze reactions with one set of enzymes in summer and another set in winter. The result is that metabolic functions of the fish are much less sensitive to long-term changes in temperature than they are to short-term changes 40.3 How do animals alter their heat exchange with the environment? -constant body temperature ( homeotherms ) or a variable body temperature ( poikilotherms ) - Ectotherms are animals whose body temperatures are determined primarily by external sources of heat. Endotherms can regulate their body temperature by producing heat metabolically or by using active mechanisms of heat loss - heterotherm is an animal that behaves sometimes as an endotherm and other times as an ectotherm (i.e. an animal that hibernates) 40.3.2 Ectotherms and endotherms respond differently to changes in temperature -Endotherms regulate their body temperature by changing how much heat they produce. Since the heat produced by living cells is a byproduct of the chemical reactions occurring in those cells, this means that the endotherm is changing its internal chemistry ( i.e. its metabolism) to regulate its temperature. -The ectotherm has not evolved a mechanism for doing this. Instead, the ectotherm regulates its body
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2-18 homeostasis - HOMEOSTASIS LIFE 40.2 40.4 40.2 How does...

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