Biology 2601: Organismal Energetics Lecture Notes PDF

Biology 2601: Organismal Physiology Energetics Energetics The study of how organisms “acquire energy, channel energy into useful functions, and dissipate energy from their bodies” Catabolism – breakdown of molecules to release energy Anabolism – use of energy to assemble molecules. Why study ene...

Biology 2601: Organismal Physiology Energetics Energetics The study of how organisms “acquire energy, channel energy into useful functions, and dissipate energy from their bodies” Catabolism – breakdown of molecules to release energy Anabolism – use of energy to assemble molecules. Why study energetics? Energy is fundamentally important to all life processes. To understand how much energy/food is needed, and how it is allocated to different activities. Energy is a major currency used to understand behavioural decisions, ecology, evolution. Dutch dream cows do not exist Plants and animals must obey the 1st and 2nd laws of thermodynamics Piersma and van Gils 2011 – The Flexible Phenotype The 1st Law Energy cannot be created or destroyed E.G. Max Rubner’s dog. – 45 days in a calorimeter. Ate 72,828 kJ of energy in food. Heat, fecal and urinary energy was 72,588 kJ. The 2nd Law of Thermodynamics Entropy (disorder) always increases - isolated vs open systems It takes energy to remain organized (alive). Plants must capture solar energy, animals must eat! What is energy? Classical mechanics – capacity to do mechanical work (force x distance) Biology? – capacity to increase order Relevant forms in biology: chemical bond energy, electrical energy, mechanical energy, heat Chemical, electrical, mechanical can do physiological work. Chemical bond energy The energy liberated or required when atoms are rearranged into new configurations. High grade, totipotent e.g. Adenosine triphosphate (ATP) phosphate bond Electrical energy The energy that a system possesses by virtue of the separation of positive and negative charges (voltage potential). High grade e.g. membrane potentials used for signalling, pumping against gradients etc. Mechanical energy The energy of organized motion in which many molecules move simultaneously in the same direction. High grade e.g. moving a limb or circulating blood Heat The energy of random atomic/molecular motion. All matter > absolute zero temperature possesses heat energy. Low grade, “waste” Determines temperature which influences physiological rates, but does not do physiological work. Energy units calorie – amount of energy (heat) to raise temperature of 1 g H2O by 1 °C Calorie = 1 kilocalorie Joule (J, SI unit). 1 calorie = 4.186 J 1 Calorie = 4.186 kJ Power – rate of energy used per unit time. 1 Watt (W) = 1 J/s. The input/output budget All absorbed chemical energy is either stored in chemical energy or eventually converted to heat. Efficiency of ATP to mechanical work ~ 25% Metabolic rate The rate at which an animal consumes energy (i.e. converts chemical energy to heat and external work). Can be measured from heat production. Calorimetry – rate of heat production, metabolic rate. Direct calorimetry Metabolic rate is measured directly from the amount of heat released by an organism. Modern devices measure heat flow electronically. Indirect calorimetry Open system Metabolic rate is calculated from the O2 consumed, the CO2 produced, or both. Stoichiometry: C6H12O6 + 6O2 6CO2 + 6H2O + 2820 kJ/mol Indirect calorimetry Open system for plants Indirect calorimetry Closed system Respiratory quotient RQ = CO2 produced/ O2 consumed Types of MRs Basal metabolic rate (BMR) – endothermic homeotherms, thermoneutral zone, fasting (postabsorptive), resting. Standard metabolic rate (SMR) – ectothermic poikilotherms, fasting, resting, at a defined temperature. Field metabolic rate (FMR) – daily energy expenditure of a free-living animal. Why postabsorptive? Specific dynamic action (SDA) is the increase in metabolic rate associated with food ingestion. Compare a small meal (red) to a large meal (green). Allometric scaling of metabolic rates Allometric scaling of metabolic rates Mass-specific metabolic rates Mass-specific metabolic rates Costs of activity Costs of locomotion – power curves Costs of locomotion – power curves Comparing locomotory costs The metabolic ceiling: multiple of BMR? Piersma and van Gils 2011 – The Flexible Phenotype