Energy Flow and Metabolism Goal of metabolism to

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

Glycolysis I

Glycolysis II

Fermentation

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

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

Entry to Krebs

Krebs Cycle

BUT. . . It almost never works that way.

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.

Phosphoenol pyruvate Pyruvate Normal Pathway To Acetyl Co. A and Krebs Cycle

Pyruvate PEP Alternate Path

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

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

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

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

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

Alpha Ketoglutarate

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

Digestion in the Florida Manatee

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

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

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

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

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