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Topic 9 How Does Life Use Energy?

Topic 9 How Does Life Use Energy?. Dr. George Lapennas Dept. of Biology. Nature of science:. Search for mechanistic explanations – ones that predict events based on underlying rules and structures. Quick review of special characteristics of living things (organisms). 1. Growth.

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Topic 9 How Does Life Use Energy?

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  1. Topic 9How Does Life Use Energy? Dr. George Lapennas Dept. of Biology

  2. Nature of science: Search for mechanistic explanations – ones that predict events based on underlying rules and structures

  3. Quick review of special characteristics of living things (organisms)

  4. 1. Growth

  5. 2. Development (changes other than growth during individual lifetime)

  6. 3. Reproduction (involves inheritance)

  7. 4. Ordered, complex structure; adaptation

  8. 5. Movement (esp. animals)

  9. 6. Sensitivity/Responsiveness

  10. 7. Evolution (change over generations)

  11. 8. Consciousness/Rationality

  12. 9. Use of energy

  13. Can life also be understood mechanistically (vs vitalistically)?

  14. An early mechanistic success: Harvey’s partial explanation of the pumping and circulation of the blood

  15. Some 19th century steps from a vitalistic toward a mechanistic understanding of life

  16. 1. The cell theory Living things are made up of large numbers of tiny units called “cells” that come from previous cells Prerequisite technical advance: Invention of the microscope (early 1600’s)

  17. Structure of an animal cell

  18. Structure of a plant cell

  19. 2. In vitro (in glass) synthesis of organic molecules Wohler’s 1828 in vitro synthesis of urea, etc. Eventually, chemists learned to synthesize everything in vitro that organisms synthesize in vivo. General conclusion: There are no unique laws of chemistry operating within living organisms.

  20. 3. The fermentation controversy “Fermentations” – chemical transformations that had only been observed in association with living things Buchner (1897) observed fermentation of fruit juice by cell-free extract of yeast, yielding alcohol and carbon dioxide (CO2) Conclusion:Living cells are not required for fermentation – only need some materials that were present within the cells (now known to be enzymes - proteins that act as catalysts to speed up reactions).

  21. 4. Cryptobiosis Does life irreversibly end when life processes cease? or … Can life processes be stopped and later re-started, so long as necessary structure have been preserved? Can the “clock” of life be stopped and then re-started?

  22. 4. Cryptobiosis Conclusion: Life processes only depend upon the presence of certain matter in a certain structural arrangement. That matter and structure can persist during drying or freezing when all processes cease. Life processes can resume upon restoration of water or thawing.

  23. Why did mechanistic explanations take so long to develop in biology? - Because living things are much more complex than anything else that scientists study - Many other discoveries had to be made before the mechanisms of biological structures and processes could be effectively investigated.

  24. Machinery of life: 4 classes of organic “macro-molecules” assembled from smaller “building blocks”

  25. Machinery of life: 4 classes of organic “macro-molecules” assembled from building blocks 1. Proteins (structural; catalytic “enzymes”) 2. Nucleic acids (DNA, RNA; instructions for inheritance as the structure of proteins) 3. Polysaccharides (energy storage; structure) 4. Complex lipids (energy storage; cell membranes)

  26. Amino acids are the building blocks of Proteins

  27. Protein structure – primary structure

  28. Protein structure – secondary structure (local folding patterns)

  29. Protein structure – tertiary structure (overall folding pattern)

  30. Protein function depends on form

  31. DNA (molecule of inheritance)

  32. Living matter seems to obey the same laws of physics and chemistry as non-living matter Conservation of mass Conservation of momentum Gravitation Chemical properties of elements Laws of thermodynamics

  33. Laws of thermodynamics In any isolated system (no matter or energy can enter or leave the system), including the entire universe: First Law – the total amount of energy is constant, though it can change form.

  34. Laws of thermodynamics In any isolated system (no matter or energy can enter or leave), including the entire universe: First Law –total amount of energy is constant, though it can change form. Second Law – Whenever anything actually happens, the entropy (disorder) of the system increases.

  35. Laws of thermodynamics • In any isolated system (no matter or energy can enter or leave), including the entire universe: • First Law –total amount of energy is constant, though it can change form. • Second Law – Whenever anything actually happens, the entropy (disorder) of the isolated system increases. • - “Time’s Arrow” points in the direction of increasing entropy (disorder) of the universe. • - Changes that would reduce the entropy of the universe cannot occur

  36. “Spontaneous” changes= changes that can happen = “downhill” changes

  37. “Spontaneous” processes can happen

  38. Two old hypotheses about animals’ use of food 1. Assimilation- food is added to the body for growth or to replace material lost through “wear and tear”

  39. Two old hypotheses about animals’ use of food 1. Assimilation - food is added to body for growth or to replace material lost through “wear and tear” 2. Combustion - food is somehow “burned” within the body, like fuel in a fire, generating heat, and being consumed in the process

  40. Reinterpretation of combustion and animal respiration by Lavoisier Lavoisier (late 1700’s)… - Overthrew phlogiston theory and applied new knowledge of gases to combustion - Flames and animals do not produce phlogiston, - Both consumeoxygen (O2) and releasecarbon dioxide (CO2) and heat

  41. Lavoisier and Laplace observed quantitative similarities between burning charcoal and the respiration of a living animal.

  42. Quantitative similarities between combustion and respiration Same/Similar ratios of … heat produced / vol. of CO2 produced and vol. of O2 consumed / vol. of CO2 produced

  43. “Slow combustion” Lavoisier and Laplace hypothesized that animals carry out a “slow combustion” of fuel (process now called cellular respiration). They believed that the function of cellular respiration was to make heat.

  44. What do we know now about the use of food by animals? - Cells both ASSIMILATE food and use it as FUEL FOR CELLULAR RESPIRATION

  45. What do we know now about the use of food? - Cells both ASSIMILATE food and use it as FUEL FOR CELLULAR RESPIRATION - For most organisms, heat is just a useless by-product of cellular respiration, not the function of the process.

  46. What is the primary function of cellular respiration? Cellular respiration provides energy to do “cell work”.

  47. What is the function of cellular respiration? Cellular respiration provides energy to do “cell work”. “Cell work” means “uphill” cellular processes that would not be spontaneous (could not occur) on their own, … but can occur if “coupled” to some other, highly spontaneous process, such that the two processes occurring together increase the entropy of the universe.

  48. 3 Types of Cell Work:-Active transport-Movement-Bio-synthesis

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