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How cells harvest energy, Princ Bio I Ch 9


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"self-feeders:. Onvert radiant energy into chemical energy
"Fed by others". Live on the energy autotrophs produce, using them as food.
aerobic respirations
when final acceptor is an oxygen molecule.
anaerbic respirations
when final acceptor is an inorganic molecule.
when final acceptor molecules is an organic molecule.
ATP Synthase
One of the most important enzymes in all living systems. Catalyzes the synthesis of ATP by using the energy store in a gradient of protons that is built across membranes.
Substrate-level phosphorylation
ATP is formed by transfering a phosphate group directly to ADP from a phosphate0bearing intermediate.
Glycolysis (basic description)
Stage one. Occurs in cytoplasm of cell. Two ATP molecules are used up early in the pathway, and four ATP are formed by substrate-level phosphorylation. This yields a net of two ATP for each molecule of glucose catabolized. End product is pyruvate
Pyruvate oxidation
pyruvate is converted to carbon dioxide. Fore each molecule of pyruvate converted, one molecules of NAD+ is reduced to NADH.
Krebs cycle
priming-prepare the six carbon molecules for energy extraction. Acetyl-CoA joins cycle and chemical groups are rearranged
Energy Extraction-four reactions
1. two carbon group from acetyl-CoA joins w/ four carbon molecules, oxaloacetate, to form a six carbon molecules citrate. Irreversible reactions. If ATP is high, krebs cycle shuts down
2 & 3.) Isomerization. OH group must be reposition. Water molecules is removed from one carbon; then water is added to different carbon. rearrangement facilitates the subsequent reactions
4.) First oxidation-
Electron Transport chain
Stage Four.
Use carbon dioxide as electron acceptor reducing CO2 to CH4 (methane) with the hydrogens derived fro organic molecules produced by other organisms
Sulfur bacteria
Prokaryotes derive energy from reduction of inorganic sulfates (SO4) to hydrogen sulfide (H2S). Hydrogen atoms are obtained from organic molecules other organisms produce. Similar to methanogens, but use SO4 as the oxidizing agen in place of CO2
Glycolysis stages
Glucose priming
Cleavage and rearrangement
-substrate-level phosphoralation
ATP generation
Glucose Priming
Three reactions "prime" glucose by changing it into a compound that can be cleaved readily into 2 three carbon phosphorylated molecules. Requires 2 ATP molecules
Cleavage and rearrangement
six carbon product from glucsoe priming is split into 2 three carbon molecules. One is G3P and the other is then converted to G3P by the second reaction.
Oxidation in glycolysis
Two electrons and one proton are transferred from G3P to NAD+, forming NADH. Both electrons in the new covalent bond come from G3P.
ATP Generation in glycolysis
four reactions convert G3P into another three carbon molecules, pyruvate. Generates two ATP molecules.

Overall reaction
4ATP (step D. 2 ATP for each G3P molecules)
-2ATP(used in the two reactions in step A)
Stage two
in mitochondria. Reduce NAD+ to NADH.
Pyruvate+NAD+ + CoA to acetyl-CoA + NADH + CO2.
metabolic breakdown of proteins fats and other lips genergate. Many metabolic processes generate it.
Used in Krebs to produce ATP. Also directed toward energy storage.
Diffusion force similar to osmosis and driven by ATP
nitrogen containing side group (amino group) is removed from amino acid in this process.

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