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Energy Flow and Metabolism

Explore the fascinating metabolic pathways of anaerobic organisms and understand the osmoregulatory mechanisms in marine invertebrates. Discover how these animals adapt to changing environments and optimize energy usage.

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Energy Flow and Metabolism

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  1. Energy Flow and Metabolism • Goal of metabolism to harvest as much useable energy as possible. • The first metabolic pathways were anaerobic pathways used by heterotrophs to break C-C bonds and gain free energy. • Skeletons of these pathways remain today. • The most ubiquitous pathways is glycolysis

  2. Glycolysis I

  3. Glycolysis II

  4. Fermentation

  5. ATP Balance • ATP is added twice to the 6 carbon sugar

  6. ATP Balance 4 ATP are produced – 2 from each of 2 3carbon fragments. Electrons are harvested as NADH is reduced.

  7. Entry to Krebs

  8. Krebs Cycle

  9. BUT . . . It almost never works that way.

  10. Example: Oysters Metabolic Shifts in Intertidal Molluscs Clams and oysters are often exposed to air with tidal changes. Valves close to prevent desiccation. Muscles must work anaerobically in a high salt environment.

  11. Normal Pathway Phosphoenol pyruvate Pyruvate To Acetyl CoA and Krebs Cycle

  12. Alternate Path Pyruvate PEP

  13. Branchpoint Enzyme PEP Pyruvate kinase is inhibited by H+ PEP Carboxykinase is favored Pyruvate Oxaloacetate

  14. Normal Volume Once Upon a Time . . . In Biscayne Bay. . . There were three copepods. Blood p = External Medium p = 1000 mOs = Cell p Cell Blood

  15. And then the rains came down . The osmolality of the external medium falls, and initially the organism swells until ions reach equilibrium

  16. Recovery In recovery blood = external medium = 800 mOs, but cells cannot reduce ion concentrations -- so free amino acids are extruded

  17. Osmoregulation in Marine Invertebraes Amino acids produced from the Krebbs cycle + ammonia in high salinity raise cell osmolarity In low salinity the amino acids are catabolized to lower osmolarity The key enzyme is alpha keto glutarate dehydrogenase which is affected by Na concentration

  18. Alpha Ketoglutarate

  19. Metabolic Pathways are also tailored to animals diet. Fats are broken down to fatty acid and enter as acetyl CoA. Proteins are deaminated and the carbon skeletons enter as PEP, pyruvate or alpha keto glutarate.

  20. Digestion in the Florida Manatee

  21. Manatee Facts • Trichechus manatus • Average length 3 meters, weight 1,200 lbs • Life span 40 years • Related to elephant • Only herbivorous marine mammal

  22. Digestion in Manatees • No front teeth, rigid pads form “lips” • Molars 6-8 in each of 4 rows • Teeth constantly replaced • Large salivary glands • Digestive tract about 120 feet in length

  23. The Digestive Tract • Like most herbivores the digestive tract is much longer than carnivores • Unique features include a cardiac caeca which secretes HCl • Mid gut caeca incubate fermenting microorganisms • A very long large intestine is a fermenting chamber

  24. Cellulose Digestion Cellulose Beta Glucans Cellobiose Glucose Acetic Acid Proprionic Acid Butyric Acid

  25. Fermentation • Both bacteria and protozoa are active in fermentation • The gut passage time of nearly 1 week allows for slow processing • Cellulose is the main component of the diet • Mixed acid fermentation produces methane, proprionic, butyric and acetic acid

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