1 14 2 Thermoregulation Body Temperature Strategy BIO 361T Fall 2014 1 Use Fourier s law to explain a why an aluminum pot at room temperature feels cold to the touch Q T L Conductivity of metals is high which means that it draws heat from an animal s warm body Q rate of heat transfer will be higher b why an animal will lose heat in cool water faster than cool air water has a higher than air so Q will be higher 2 Most homeotherms maintain a relatively constant Tb by thermoregulating How could an animal be homeothermic without any thermoregulatory mechanisms If Ta is fairly constant like for animals in temperate environments then Tb will be fairly constant without any effort on the animal s part An animal s body temperature strategy may change with its environment For example a goldfish kept in a home aquarium will be homeothermic by default If it is put in a pond it will be poikilothermic due to its physiology 3 An Antarctic fish is metabolically efficient at Ta 1 96 C but will die a few degrees above this a Is this fish a eurytherm or stenotherm Stenotherm recall euryhaline and stenohaline which refer to salinity tolerance b In molecular terms why does the fish die if Ta increases slightly Hydrophobic bonds strengthen and van der Waals forces and hydrogen bonds are disrupted This causes changes in protein structure and enzymes will denature They will be unable to catalyze reactions Even though the rate of chemical reactions uncatalyzed will increase it will be insufficient to support cellular function Proteins that have non enzymatic functions motor proteins structural proteins channels will also denature and the animal s cellular functions will fail 4 For many enzymes a 10 C increase in temperature doubles Vm This is described as the Q10 value If Vm doubles with a 10 C increase Q10 2 a What does it mean if the Q10 3 Reaction rate triples with a 10 C increase in temperature b What will happen to an enzyme whose Q10 2 if the temperature drops 10 C It will decrease by 50 assume that this function is linear c Imagine the enzymes for cellular respiration have a Q10 of 2 How will this affect a poikilotherm s ability to make ATP when Tb decreases ATP synthesis will decrease by half 2 d What will be the effect if the ATP dependent processes in the poikilotherm also have a Q10 of 2 ATP use will also decrease by half so the animal will not be adversely affected Problems potentially arise when enzymes have mismatched Q10 values If enzymes in cellular respiration had a Q10 of 3 but the Q10 of enzymes that use ATP were 2 the animal s cells would use ATP faster than it is being produced It would require other mechanisms to compensate for this such as changing substrate concentrations or allosterically regulating enzymes 5 Stearic acid and oleic acid are both 18 carbon fatty acids but the melting point of stearic acid is 69 C while that of oleic acid is 12 C a Why are these melting points drastically different Oleic acid is less saturated than stearic acid oleic acid has one double bond stearic acid has none b Which fatty acid would you expect to find in the membrane of an animal in the Sahara Desert Explain your answer More stearic acid More saturated fatty acids are less fluid because they pack more tightly In an animal in a hot climate the membrane is in danger of being too fluid so it will remodel its membranes to be stiffer use saturated fatty acids like stearic acid c What polar head group would you expect to find attached to these fatty acid tails in the same animal Explain your answer Phosphatidylcholine Its shape reduces fluidity instead of phosphatidylethanolamine 6 The following graph shows differences in fatty acid composition of membranes in cells taken from several areas on a reindeer the proximal middle and distal portions of the forelegs and the proximal middle and distal portions of the hindlegs a Explain the difference in stearic acid vs oleic acid composition in the legs in general The reindeer is adapted to its cold climate so it has more unsaturated fatty acids like oleic acid to maintain membrane fluidity b Why does this difference increase farther from the body distal compared to proximal Tb will be lower in the extremities so there is a greater need for poikilothermic adaptations like more unsaturated fatty acids to maintain membrane fluidity c Explain the difference in palmitic acid vs stearic acid composition The numbers indicate number of carbons Palmitic acid is shorter so it will pack less tightly and make the membrane more fluid
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