Today Q10 revisited Enzyme adaptation Biochemical Adaptation to Temperature Change – enzymes, membranes and heat shock proteins Mechanics of heat gain and loss Convection Conduction Evaporation Radiation Definitions of the “therms” Keeping Warm --- the extremes

Q10 is a measure of how much the rate of a process changes with temperature. Q 10 = (Rate of Process at Temp 2/Rate of Process at Temp 1 ) 10/(Temp 2 – Temp 1) When the temperature change is 10oC, then Q10 = Rate2 /Rate1

Strategies for Temp Adjustment 1. Quantitative – Have more enzyme to use at lower temps. 2. Qualitative – Produce enzymes with different thermal modulations

Here we have a population of frogs acclimated to 25oC and one acclimated to 5oC. The population acclimated to cold shows an increased metabolic rate – even over a range of temperatures. However the slopes of the red and blue lines are not the same.

The upper chart shows the Q10 for the cold adapted frog with Q10s of 1 The upper chart shows the Q10 for the cold adapted frog with Q10s of 1.5 and 1.6, over the same range the warm adapted frog shows Q10s of 2.2 and 2.8. We conclude that the enzymes involved have been modulated qualitatively in the process of adaptation.

Km of PEP for the enzyme pyruvate kinase in fishes living in different climates. The lowest Km – most efficient binding of substrate and enzyme is correlated with the temperature of acclimation.

Membrane viscosity also affected by temperature.

Membrane Changes In heat – more cholesterol, more satuated fatty acids In cold – more polyunsaturated fatty acids (PUFAs),

Stress Proteins or Heat Shock Proteins are produced when an organism is subjected to environmental stresses including heat, high salinity, desiccation, heavy metal pollution. Hsp 70 and hps 60 proteins act to protect enzymes by folding around them to prevent changes in weak bonds and denaturation.

Two snails, Tegula funebralis and Tegula brunnea are subjected to a shift to 30oC. The intertidal form T. brunnea responds with the production of HSPs, This is a from that lives intertidally and is subject to more frequent temp changes.

Mechanisms of Heat Exchange

Conduction varies with the area exchanging heat, the distance between the source and the sink and the types of materials in contact. Q = kA(t2-t1) l

Convection is the special case of conduction where one or both of the exchangers are fluid and moving. In animal systems, concurrent conduction systems are modified to form very efficient counter current systems.

Radiation Bodies radiate electromagnetic energy proportional to the 4th power of the absolute temperature of the surface. The hotter the surface, the shorter the wavelength radiated. At biological temperatures, approximately 300oK, our bodies emit energy in the infrared range.

Evaporation One of the most effective ways to loose heat is to use it to heat water from a liquid to a gaseous state. This requires a lot of heat energy, 585 calories/ gram. Many animals sweat, or pant to remove heat. Camels will sweat when they are well watered, but a dry camel instead allows it body temperature to fluctuate + 3.5o.

Extremophiles – bacteria, diatoms and protozoa have been found living in sea ice in the arctic and antarctic. The presence of these organisms suggests that there may also be live on ice covered plants like Europa shown here.