BIOL1131 Lecture 3.2 Metabolism & Movement 2024 PDF

BIOL1131 Plant and Animal Biology Lecture 4.2 Metabolism, Energetics and Movement See also (in the Biological Sciences Library) Comparative Animal Physiology (P. C. Withers, 1992) or Animal Physiology ( K. Schmidt-Nielsen, 199...

BIOL1131 Plant and Animal Biology Lecture 4.2 Metabolism, Energetics and Movement See also (in the Biological Sciences Library) Comparative Animal Physiology (P. C. Withers, 1992) or Animal Physiology ( K. Schmidt-Nielsen, 1997) Cell metabolism Cell Metabolism is the use of energy & catabolism (breakdown) / anabolism (synthesis) of organic molecules Animal metabolism Cell Metabolism is the use of energy and catabolism/anabolism of organic molecules Animal metabolism is the overall direction of biochemical reactions; it defines animal ‘life’; it produces heat “THE FIRE OF LIFE” Metabolism & physics Cell Metabolism is the use of energy and catabolism/anabolism of organic molecules. Animal metabolism is the overall direction of biochemical reactions; it defines animal ‘life’ Physical laws dictate energy exchange & transformation in all reactions (including biological ones), so important for biologists to understand the physical laws of energy & heat exchange Conservation of energy Metabolism & the fire of life Cell Metabolism is the use of energy and catabolism/anabolism of organic molecules. Animal metabolism is the overall direction of biochemical reactions; it defines animal ‘life’ Physical laws dictate energy exchange & transformation in all reactions (including biological ones), so important for biologists to understand the physical laws of energy & heat exchange Metabolic rate of animals depends on a number of factors, including presence of: – oxygen – activity level – body mass – cellular complexity, phylogeny – body/ambient temperature ATP & energy Adenosine triphosphate (ATP) ATP is a high-energy molecule used by cells as energy source by losing phosphate groups Phosphate x3 Adenosine ATP → 22 kJ useful energy / mol Also used for DNA & RNA coenzyme Anaerobic (Glycolytic) Metabolism Glucose → 2 lactate + 2 ATP + 45 kJ/mole useful energy + 72 kJ/mole heat energy = 117 kJ/mole lactate Aerobic (O2) Metabolism Glucose + 6 O2 → 6 CO2 + 6 H2O + 32 ATP + 1161 kJ/mole useful energy + 1693 kJ/mole heat energy = 2870 kJ/mole Where did O2 come from? Atmosphere contained no O2 at first First photosynthetic bacteria were anaerobic - metabolism did not use O2; trapped sunlight energy used to synthesise organic molecules from CO2 From 2 BYBP plants produced O2 as a by-product, accumulated to current level of 21% atmosphere Animal metabolism Animal metabolism is sum-total of all biochemical reactions occurring in the body of an animal – Or subsets thereof, eg for glucose metabolism If the metabolic rate of an animal is a measure of its overall cellular metabolism, then how is it measured? Metabolic rate measurement Glucose + 6 O2 → 6 CO2 + 6 H2O + 2870 kJ/mole There are a variety of possible ways to measure metabolic rate: 1. heat production 2. oxygen consumption 3. carbon dioxide production 4. energy balance (IN = OUT) 5. substrate utilisation 6. metabolic water production Metabolic rate measurement 1. Heat production Best measure of metabolic rate? Antoine Lavoisier (1743-1794) Named oxygen and hydrogen Helped create metric system, first law thermodynamics Measured direct heat production using a simple but ingenious method Internal External ice jacket ice jacket Dripping Rate = metabolic heat production Metabolic rate measurement 2. Oxygen consumption 3. Carbon dioxide production Measurement of O2 consumption CO2 production possible Lavoisier in 1770’s CO2 = V4 O2 consumed = V1 – V4 Metabolic rate measurement 4. IN-OUT energy balance It is possible to determine the metabolic rate of an animal by its overall energy balance Food Drink Faeces Urine Growth Reproduction Unaccounted energy = metabolic energy Determinants of metabolic rate 1. Activity Level 2. Body Mass 3. Taxonomy 4. Temperature Determinants of metabolic rate 1. Activity Level k Metabolic rate varies from Minimal / basal level to Maximal / summit level Determinants of metabolic rate 2. Body Mass Relationship between body mass & metabolic rate Does a bigger animal have a higher or lower metabolic rate than a smaller animal? Determinants of metabolic rate – body mass Some books suggest smaller animals have a lower metabolic rate Relationship is a curve Determinants of metabolic rate – body mass The curve can be converted to a straight line using a logarithmic scale for both axes The slope of the log-log relationship is 0.75 Why? Unknown mystery! Slope = 1.0 Slope = 0.75 Slope = 0.67 Determinants of metabolic rate – body mass Possible reasons include 0.75 is a 'compromise’ 1.0 = metabolism proportional to mass 0.67 = metabolism proportional to surface area Theoretical slope in 4-dimensional space (length, breadth, depth, time) is 0.75 the slope is 0.67 in three dimensional space (length, breadth, depth). Fractal scaling, or patterns of shape. etc…… Unfortunately, none of these is convincing! Determinants of metabolic rate – body mass WARNING!! Many text books may suggest smaller animals have a higher metabolic rate But this is metabolic rate per gram of body mass! Determinants of metabolic rate – body mass Many physiological processes proportional to metabolic rate, not body mass ‘Metabolic mass’ is the physiologically-related “mass” It changes less rapidly than actual body mass mouse human elephant MASS 0.010 kg 60 kg 5000 kg 0.03 21.6 595 'METABOLIC MASS' (0.0100.75) (600.75) (50000.75) A terrible mistake: LSD and elephants … Tusko, male Asian elephant, Lincoln Park Zoo, Oklahoma City Drug dose dependence is a classic example of the importance of non- linear metabolism-mass relationship Effects of many drugs are proportional to metabolic rate, not body mass Change mouse : elephant mass 500,000x metabolic rate 20,000x Dose 25x too high! West et al 1962 Science 138, 1100- Determinants of metabolic rate 3. Cellular Grade Same effect of mass on metabolism for almost all animals slope = 0.75 However, metabolic rate varies dramatically for three groups of animals: Unicellular organisms Single- vs multicellular Poikilotherms / cell surface area grade ‘cold-blooded’ animals Homeotherms / ‘metabolic grade’ + temperature ‘warm-blooded’ animals ”metabolic grade” + body temperature “cell surface area grade” Determinants of metabolic rate 4. Temperature Chemical reactions are (exponentially) faster at higher temperatures Q10 = proportional increase in reaction rate (K) over 10°C range For physical reactions, like diffusion, Q10 ≈ 1.1 For biochemical reactions & biological processes, Q10 ≈ 2 - 3. More later Determinants of metabolic rate 5. Activity Locomotion has a major 109 kmh metabolic cost Aquatic = swimming 130 kmh Terrestrial = running Aerial = flying 389 kmph Animal locomotion grams The ‘motor’ changes with size Muscles Cilia (many) True flagella (undulate) Bacterial flagella (rotate) grams Animal locomotion Animal locomotion Aquatic (swimming) Terrestrial (slithering, walking) Aerial (gliding and flying) Terrestrial locomotion is based on lever mechanics (usually) Aquatic & Aerial locomotion have similar fluid- dynamics (surprisingly?) similar concept swimming (water) is based on drag flying (air) is based on lift Animal locomotion – swimming Animals can swim by a variety of means, including Jet propulsion – squeezing water out of a chambre Drag from limbs, body or fin undulations ‘Flying' using lift Animal locomotion – swimming Jet propulsion Jellyfish (Cnidaria) Circular muscles around bell Cephalopods (Mollusca) Octopus, squid, cuttlefish Circular muscles around mantle, siphon for direction Bivalves (Mollusca) Scallops Adductor muscles pull shells together, forces water from the shells Animal locomotion – swimming Drag from Limbs, Body, Fins Drag in water counteracted by thrust Like a rowing oar, limbs, fins & bodies push back on water; drag provides forward force Diving beetle: Aquatic frog: Pelagic fish: hairy legs finned feet Tail fin Animal locomotion – swimming Flying underwater Less common Uses hydrofoil (≈ ‘wing’) to create lift for propulsion ‘Flying’ only works for relatively big aquatic animals Penguins Turtles Plesiosaurs Animal locomotion – flying Flying (aquatic & aerial) uses a fluid dynamic force: ‘ lift ’ Counterbalances weight, overcomes drag of the animal Animal locomotion – flying Parachuting A 'primitive' form of flight Drag slows fall of object Parachuting similar 'rowing‘ (drag) Can be turned into gliding (+ lift) Various animals glide (SE Asia!): Frogs Snakes Lizards Birds Also plant seeds Animal locomotion – flying Gliding uses part of the lift force to overcome drag So the animal maintains speed But insufficient lift to balance weight So animal moves forward horizontally & descends Gliding uses less energy than powered flight Animal locomotion – flying Gliding mammals: evolved multiple times Flying squirrel Flying lemur Sugar glider Animal locomotion – flying Soaring birds: evolved multiple times Albatross Vulture – dynamic soaring – thermal soaring Animal locomotion – flying Powered flight Flying animals provide extra energy through their wing movements (muscle contraction) to maintain their horizontal position (lift = body weight) and forward velocity Animal locomotion – flying Evolution of Powered Flight – 2 ways Ground up: Tree down: ‘leaping’ dinosaurs ‘gliding’ mammals Climbing Running Gliding Leaping Flying Flying Animal locomotion – running Running / walking Limbs (‘levers’) support / lift body off ground & provide forward movement Lift pattern can confer stability: centre of mass held in tripod formed by three limbs contacting ground Animal locomotion – running Metabolic cost of walking/running is typically linear with speed (especially by appropriate gait selection) The net cost of transport (slope of line) is independent of speed. Slope = NCOT (net cost of transport) Animal locomotion – hopping Hopping animals, eg kangaroos, have wide range of speeds with no effect on the metabolic cost Tendons act like springs; store elastic energy for re-bound Hopping at high speed is very economical Animal locomotion – metabolic cost Transport costs vary with body mass, speed & locomotion type More economical per gram for large animals Most economical for swimmers, least economical for runners Running animals Flying animals Swimming animals