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Controlling the Internal Environment I - Regulation of Body Temperature

Keywords (reading p. 925-930). Temperature effectsOn reactionsOn lipid bilayerEndothermEctothermHomeostasisThermoregulationBehavioral thermoregulation. Physiological thermoregulationCountercurrent heat exchangeShiveringEffect of large sizeinsulation. Temperature. Affects the rates of reactions and the characteristics of macromoleculesSince organisms are machines made of macromolecules in which chemical reactions occur, temperature is an very important environmental feature.

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Controlling the Internal Environment I - Regulation of Body Temperature

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    1. Controlling the Internal Environment I - Regulation of Body Temperature

    2. Keywords (reading p. 925-930) Temperature effects On reactions On lipid bilayer Endotherm Ectotherm Homeostasis Thermoregulation Behavioral thermoregulation Physiological thermoregulation Countercurrent heat exchange Shivering Effect of large size insulation

    3. Temperature Affects the rates of reactions and the characteristics of macromolecules Since organisms are machines made of macromolecules in which chemical reactions occur, temperature is an very important environmental feature

    4. Temperature affects the rates of reactions, e.g. enzyme catalyzed reaction

    5. Illustrated by gas molecules in a balloon slowing down if they are cooled

    6. What is the magnitude of temperature effects for physiological processes or biochemical reactions? Increase by 2-3 fold for a 10C increase in temperature. Q10 value = 2 to 3

    8. Q10 values differ for different physiological processes or biochemical reactions Some will speed up more, some less This can ruin coordination of enzymes and reactions in metabolism, e.g., mitochondria

    9. Temperature affects characteristics of macromolecules Example: lipid bilayer

    10. Lipid bilayer

    11. Structure of an unsaturated phospholipid

    12. Bilayer with unsaturated phospholipid stays fluid at lower temperatures

    13. Maintaining membrane fluidity at different temperatures

    14. Melting temperatures of some saturated fatty acids

    15. Melting temperature of some unsaturated fatty acids

    16. Fatty acid composition of membranes from animals acclimated to different temperatures

    17. Ratio of saturated to unsaturated

    18. Ratio of saturated to unsaturated

    19. Regulation of desaturase activity Desaturase is a membrane associated protein Under high temperature conditions, high fatty acid saturation Under low temperature, increased unsaturation

    21. Desaturase in Tetrahymena Phospholipids are constantly cycled into the lipid bilayer. Exposed desaturase will form unsaturated PLs that will then go into bilayer increasing fluidity

    22. Lipid protein interactions Example: The chemical characteristics of milk

    25. Curdling of milk

    26. The making of whipped cream and butter

    27. Since temperature has such a fundamental influence on biochemistry and physiology, animals: A. regulate their body temperatures so they arent affected by temperature or can live under a wide range of conditions B. Dont regulate their temperature and accept metabolic consequences or live under small range of conditions

    28. Endotherms vs. Ectotherms Ectotherms have a body temperature the same as their environment Endotherms use heat from metabolism When endotherms are able to regulate their temperature they are called homeotherms

    29. Example of endotherm and ectotherm

    30. Homeostasis The steady-state physiological condition of the body Internal fluctuations are small

    31. Thermoregulation Regulation of body temperature Can be behavioral or physiological

    32. Behavioral thermoregulation

    33. Brandt's Cormorants, Phalacrocorax penicillatus, taking advantage of coastal morning sunlight.

    35. Example of physiological: countercurrent heat exchange

    36. Arteries and veins in appendages are closely associated Hot arterial blood passes heat to returning venous blood. No heat is lost

    37. Blood vessels in a bird leg

    38. Similar mechanism in flippers of marine mammals

    39. Blood flow can be controlled so that heat is lost. Blood goes to alternate veins close to the surface.

    40. Countercurrent exchange is a trick used by many animals

    41. Tuna heat exchanger

    42. Great white shark

    44. Other tricks: shivering Non-shivering thermogenesis: brown fat Using ATP to contract muscles releasing heat instead of movement

    45. Brown fat-short circuited mitochondria

    46. 5% in human infants

    47. Insect preflight warmup

    49. Another trick: reduce heat loss Large size - reduced surface area relative to volume prevents heat from escaping Insulation - e.g., fur, feathers Big problem for marine mammals since they have high body temp. and water conducts heat faster than air

    50. Insulating fat (blubber)

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