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a partial degradation of sugars or other organic fuel that occurs without the use of oxygen
oxygenis consumed as a reactant along with the organic fuel
Organic compounds + Oxygen -> Carbon dioxide + Water + Energy
Some prokaryotes use substances other than oxygen as reactants in a similar process that harvests chemical energy without oxygen
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
transfer of one or more electrons (e-) from one reactant to another
the loss of electronsfrom one substance
- reducing agent - electron donor
- oxidizing agent - electron acceptor
the addition of electrons to another substance
- 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
The enzymatictransfer of 2 electrons and 1 proton (H+) from an organic molecule in food to NAD+ reduces the NAD+ to NADH
The Stages of Cellular Respiration
- Citric acid cycle and pyruate oxidation
- Oxidative phophorylation : electron transport and chemiosmosis
- 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 CoAGlycolysis occurs whether or not O2 is present
Glycolysis ( Review)
- 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+
- 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
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
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.
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
A smaller amount of ATP is formed directly in a few reactions of glycolysis and the citric acid cycle by a mechanism
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?)
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)
->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.
- 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
energy stored in the form of a hydrogen ion gradient across a membrane is used to drive cellular work such as the synthesisof ATP
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)
- 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
- 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
lactic acid fermentation
- pyruvateis reduced directly by NADH to form lactate as an endproduct, with no release of CO2.
- -human muscle cells make ATP
carry outonly fermentation or anaerobic respiration.
organism, like yeasts and many bacteria, can make enough ATP to surviveusing either fermentation or respiration
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.
breaks the fatty acids down to two-carbon fragments, which enterthe citric acid cycle as acetyl CoA.
- Metabolism is versatile and adaptable
- compounds formed as intermediate stage can be diverted to anabolic pathways which cell can synthesize the molecules it required.
- 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.