Lecture 3 (Sept 12) PDF

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These are notes for the third lecture, the notes are very thorough and entail all the information discussed in class....

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LECTURE 3: PRINCIPLES OF THERMAL BIOLOGY 1. Temperature - a measure of the speed or intensity of the incessant random motions that all the atoms and molecules of any substance undergo on an atomic-molecular scale - more exactly, the temperature of a substance is proportional to the product of the mean square speed of the random molecular motions and the molecular mass - cultural and behavioural activities that allow us to withstand extremes - is the intensity of the motion of the atoms inside the object - things can. Be the same temperature but have different amounts of heat - heat - amount of energy in an object - temperature determines the direction of heat transfer - warm to cool - temperature changes can be very tough on an organism 2. Thermal biology - metabolic rate is dependent on body temperature - as the body temperature goes up, the metabolic rate goes up exponentially - Q10 : the temperature coefficient - the ration of the rate f a process at one temperature over the rate of the same process at a temperature 10 degrees lower - because the temperature-metabolic rate relationship is not exactly exponential, the impact of a change of temperature varies with temperature - = about 1 for many physical/ chemical processes - = about 2-3 for most biological processes - how do these temperature changes occur? - temperature determines motion and therefore the rate at which molecules encounter one another - more interactions = more reactions - temperature also determines the conformation and efficiency of enzymes (Q10 = about 2-3 in biological systems)

3. Definitions: - endotherms: warm themselves by generation of internal metabolic heat - ectotherm: rely mostly on external temperatures to determine body temperature (Tb) - homeotherms: maintain a constant body temperature - poikilotherms: allow Tb to vary - heterotherms: have more than one temperature set point, or switch between homeo and poikilothermy - regional endotherms/ heterothermy: different Tb in different parts of the body

4. Enzymes: - how enzymes work - temperature can affect the rate at which the substrate and enzyme encounter one another - warmer = more often = more reactions - substrate + enzyme —> products - the enzymes’s active sit can change shape with temperature - change in binding affinity for substrate (generally warmer=weaker) - temperature can affect the tertiary structure of an enzyme - enzyme has a optimum temperature - more likely to act with its substrate - increases to optimum temperature and then decreases sharply - at warmer temperatures enzymes have a weaker binding affinity for their substrate - Km is a property of the enzyme - varies with temperature - is the amount of substrate required to reach 50% of Vmax - a function of tertiary protein structure and therefore temperature - Vmax = maximum rate of reaction - Kcat: number of molecules of substrate processed per unit time at saturation - high Km = low affinity - low Km = high affinity - how does affinity change with temperature? - affinity too high: enzyme binds too tightly to substrate = slow reactions - affinity too low: enzyme binds too loosely to substrate = reactions less likely to happen 5. List of processes in ectotherms are governed by temperature - metabolic rate - activity levels - muscle contraction - locomotive speed - digestion - growth - germination - photosynthesis - fruit production and ripening - going with the flow is better in some places than others 6. Behavioural thermoregulation - changing your behaviour allows maintenance of body temperature - basking in the sun - shade

7. Three important terms - adaptation (evolutionary) - example: alpine vs lowland plants - acclimatization (in field) - example: summer vs winter - acclimation (in lab) - cool vs warm grown plants 8. Compensation - maintain performance in the face of varying conditions - requires a shift away from the acute response - plasticity on the order of hours to days to weeks - works through... - changing enzymes in a pathway - amount of enzyme - version of enzyme (lysozyme) - phosphorylation - change they enzyme’s environment 9. Changing the activity of an enzyme will alter the rate of the reaction - abundance of the enzyme - enzyme produced - phosphorylation of an enzyme can activate it, change its conformation or alter activity - mediated by protein kinases - changing the enzyme’s environment: - lipid environment - pH - substrate availability 10. Phospholipid membrane changes contribute to compensation - homeoviscous adaptation - maintain the same viscosity across teh temperatures - short chain lengths increase fluidity - incorporating double bonds increases fluidity - changing head-groups changes fluidity - the membrane environment affects transmembrane ion function, as well...