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fermentation
a partial degradation of sugars or other organic fuel that occurs without the use of oxygen
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aerobic respiration
oxygenis consumed as a reactant along with the organic fuel
Organic compounds + Oxygen -> Carbon dioxide + Water + Energy
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anaerobic respiration
Some prokaryotes use substances other than oxygen as reactants in a similar process that harvests chemical energy without oxygen
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degradation of the sugar glucose (C6H12O6):
C6H12O6 + 6O2 ->6 CO2 + 6 H2O + Energy (ATP +heat)
- breakdown of glucose is exergonic, having a free energy change of -686 kcal (2,870 kJ) per mole of glucose decomposed (ΔG=-686 kcal/mol).
- 34% of the potential chemical energy in glucose has beentransferred to ATP
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redox reactions
transfer of one or more electrons (e-) from one reactant to another
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oxidation
the loss of electronsfrom one substance
- reducing agent - electron donor
- oxidizing agent - electron acceptor
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reduction
the addition of electrons to another substance
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NAD+
- an electron carrier, a coenzyme, an electron carrier because it can cycle easily between oxidized (NAD+) and reduced (NADH) states
- a single molecule of NADH generates enough proton-motive force for the synthesis of 2.5 ATP
- FADH -> 1.5 ATP
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Dehydrogenase
The enzymatictransfer of 2 electrons and 1 proton (H+) from an organic molecule in food to NAD+ reduces the NAD+ to NADH
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The Stages of Cellular Respiration
- Glycosis
- Citric acid cycle and pyruate oxidation
- Oxidative phophorylation : electron transport and chemiosmosis
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Glycolysis
- a series of chemical reactions in the cytoplasm of a cell that breaks down glucose into two molecules of pyruvic acid
- 4 atp produced, 2 atp used, 2 net ATP, 2 NADH molecules are produced.
- Intermediate Stage - eukaryotes, pyruvate enters the mitochondrion combine with coenzyme A and is oxidized to a compound called acetyl CoA
- Glycolysis occurs whether or not O2 is present
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Glycolysis ( Review)
- Glucose
- 2 ADP + 2 P <- 2 ATP used (energy investment)
- 4 ADP + 4P -> 4ATP formed
- (2NAD+) + (4e)- + (4H+) -> (2NADH) + (2H+)
- Net : 2 pyruvate + 2H2O, 2 ATP, 2NADH + 2H+
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acetyl CoA
- Upon entering the mitochondrion via active transport, pyruvateis first converted to a compound called acetyl coenzyme
- 1) Pyruvate oxidized -> CO2
- 2)Form acetate, oxidized e- convert NAD+ -> NADH
- 3)acetate(pyruate acid) + CoA -> acetyl CoA
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Citric acid cycle
- A series of reaction that breaks down Acetyl-CoA to form 2 ATP, 3 NADH, 1 FADH2
- CO2 is by product
- similar to Calvin Cycle
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Citric Acid Cycle
[Acetyl CoA] -> [Citrate (6 CO2)] -> [NAD+ -> NADH + H] -> [Ketogutaric acid (4CO2)] -> [ADP ->ATP] + [NAD+ -> NADH + H] -> [Succinic Acid] -> [FAD -> FADH2] + [NAD+ -> NADH + H] -> Oxaloacetic Acid
- Step 3,4,8 -> 3 NAD+ produced
- Step 6 -> FADH2 produced
- Step 5 -> ATP produced by substrate-level phosphorylation.
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oxidative phosphorylation
The energy released at each step of the chain is stored in a form the mitochondrion (or prokaryotic cell) can use to make ATP from ADP
Electron transport chain + Chemiosmosis
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substrate-level phosphorylation
A smaller amount of ATP is formed directly in a few reactions of glycolysis and the citric acid cycle by a mechanism
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electron transport chain
proteins, built into the inner membrane of the mitochondria of eukaryotic cells and the plasma membrane of aerobically respiring prokaryotes.NADH to the “top,” higher-energy end of thechain. At the “bottom,” lower-energy end, O2 captures these electrons along with hydrogen nuclei (H), forming water.glucose → NADH →electron transport chain → oxygenDownhill -> become oxidized FADH2 and NADH carry electrons to chain O2 binds with H to form H2O -> releasing 32 or 30 ATP! (36?)
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flavoprotein -> ubiquinone ->
- 1)Electrons removed from glucose by NAD, during glycolysis and thecitric acid cycle, are transferred from NADH to the first moleculeof the electron transport chain
- 2) a small hydrophobic molecule, the only memberof the electron transport chain that is not a protein. (CoQ)
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->cytochromes -> cytochrome of the chain, cyt a3
- Most of the remaining electron carriers between ubiquinone and oxygen are proteins
- heme group
- 2) very electronegative.Each oxygen atom also picks up a pair of hydrogen ions fromthe aqueous solution, forming water.
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ATP synthase
- the enzyme that actually makes ATP from ADP and inorganic phosphate
- smallest molecular rotary motor known
- proton motive force, emphasizing the capacity of the gradient toperform work.
- consists of a number of polypeptide subunits
- drive by chemiomosis
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chemiosmosis
energy stored in the form of a hydrogen ion gradient across a membrane is used to drive cellular work such as the synthesisof ATP
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anaerobic respiration (more)
- “sulfate-reducing” marine bacteria, for instance,use the sulfate ion (SO42) at the end of their respiratorychain instead of oxygen
- the final acceptoris another molecule that is electronegative
- Has ETC(cellular respiratory)
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Fermentation
- a process follows Glycolysis when oxygen is present
- transfer electrons from NADH to pyruvate, the end product of glycolysis.
- no ETC
- Final electron acceptor is organic molecule like pyruvate(lactic)/acetaldehyde(alcohol)
- -Lactic acid fermentation
- -Alcoholic fermentation
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alcohol fermentation
- pyruvate is converted to ethanol (ethyl alcohol) in two steps
- Pyruvate -> CO2 -> Acetaldehyde(2carbon) -> enthanol by NADH
- produce CO2 and Ethy alcohol, 2ATP
- used by yeast cells
- brewing, winemaking, and baking
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lactic acid fermentation
- pyruvateis reduced directly by NADH to form lactate as an endproduct, with no release of CO2.
- -human muscle cells make ATP
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obligate anaerobes
carry outonly fermentation or anaerobic respiration.
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facultative anaerobes
organism, like yeasts and many bacteria, can make enough ATP to surviveusing either fermentation or respiration
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The catabolism of various molecules
- Proteins -> Amino acids -> Glycolysis(Pyruvate)
- Carbohydrates -> sugars -> Glycolysis(Glucose)
- Fats-> Glycerol ->Glycolysis(Glyceraldhyde-3)
- -> fatty acids (beta oxidation)-> Acetyl Coa
- Fat produce twice as energy as Carb.
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beta oxidation
breaks the fatty acids down to two-carbon fragments, which enterthe citric acid cycle as acetyl CoA.
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Biosynthesis
- Metabolism is versatile and adaptable
- compounds formed as intermediate stage can be diverted to anabolic pathways which cell can synthesize the molecules it required.
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Phosphofructokinase
- adjuststhe rate of respiration as the cell’s catabolic and anabolic demands change.
- the enzyme that catalyzes step 3 of glycolysis
- inhibited by ATP(accumulated) and stimulated by AMP -> slow down glycolysis
- citrate accumulates in mitochondria, some of it passes into the cytosoland inhibits phosphofructokinase.
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