Amazoniac
Member
Some time ago the cry-baby here tried to find animations of the process of cellular respiration for a more realistic perspective. What's discussed below not being evident in them just shows how limiting these concepts can be and how dependent it all is on dusty textbooks.
↳ Mitochondrial pathways to Complexes I&II: convergent electron transfer at the Q-junction and additive effect of substrate combinations (attached file is a version of the whole document)
Ordering complexes is dangerous, should be reconsidered as drugs.
My selection was toxic, read the rest.
- MitoPedia: MiP concepts - Bioblast
- Cellular respiration - Wikipedia
- electron transport chain substrates inhibitors | Google Images (for the experiments)
↳ Mitochondrial pathways to Complexes I&II: convergent electron transfer at the Q-junction and additive effect of substrate combinations (attached file is a version of the whole document)
"The term ‘electron transfer chain’ (or electron transport chain, ETC) is a misnomer. Understanding mitochondrial respiratory control has suffered greatly from this inappropriate terminology, although textbooks using the term ETC make it sufficiently clear that electron transfer systems are not arranged as a chain: the ‘ETC’ is in fact not a simple chain but an arrangement of electron transfer complexes in a non-linear, convergent electron transfer system (ETS; Fig. 6.1)."
"The convention of defining the electron transfer chain as being comprised of four respiratory complexes has conceptual weaknesses. (a) In fact, there are at least six Complexes of mitochondrial electron transfer: In addition to Complexes I and II, the Complexes glycerophosphate dehydrogenase (CGpDH) and electron-transferring flavoprotein (CETF) are involved in electron transfer to Q and Complex III (Fig. 6.2). (b) The term ‘chain’ suggests a linear sequence, whereas the functional structure of the electron transfer system can only be understood by recognizing the convergence of electron flow at the Q-junction, followed by a chain of Complexes III and IV, mediated by cytochrome c (Fig. 6.1 and 6.2)."
"The concept on convergent electron transfer at the Q-junction (ETS) challenges conventional OXPHOS analysis based on the ETC terminology and a way of thinking about the mitochondrial ‘electron transfer chain’ (Fig. 6.2)."
"Electrons flow™ to oxygen from either Complex I (CI) with a total of three coupling sites in the N-pathway, or from Complex II (CII) and other flavoproteins, providing multiple entries into the Q-cycle with two coupling sites downstream." "When the TCA cycle is in full operation in the living cell with influx of pyruvate, electron flow into the Q-junction converges according to a NADH:succinate ratio of 4:1 (Fig. 6.4)."
"A rapidly growing number of studies on various tissues and cells points to the importance of the additive effect of substrate combinations on OXPHOS-capacity (Gnaiger 2009). Convergent electron flow to the Q-junction in the NS-pathway resolves discrepancies between living cells and mitochondria. This additive effect indicates a high downstream excess capacity of respiratory complexes including cytochrome c oxidase (CIV) over Complexes CI and CII."
"The convention of defining the electron transfer chain as being comprised of four respiratory complexes has conceptual weaknesses. (a) In fact, there are at least six Complexes of mitochondrial electron transfer: In addition to Complexes I and II, the Complexes glycerophosphate dehydrogenase (CGpDH) and electron-transferring flavoprotein (CETF) are involved in electron transfer to Q and Complex III (Fig. 6.2). (b) The term ‘chain’ suggests a linear sequence, whereas the functional structure of the electron transfer system can only be understood by recognizing the convergence of electron flow at the Q-junction, followed by a chain of Complexes III and IV, mediated by cytochrome c (Fig. 6.1 and 6.2)."
"The concept on convergent electron transfer at the Q-junction (ETS) challenges conventional OXPHOS analysis based on the ETC terminology and a way of thinking about the mitochondrial ‘electron transfer chain’ (Fig. 6.2)."
"Electrons flow™ to oxygen from either Complex I (CI) with a total of three coupling sites in the N-pathway, or from Complex II (CII) and other flavoproteins, providing multiple entries into the Q-cycle with two coupling sites downstream." "When the TCA cycle is in full operation in the living cell with influx of pyruvate, electron flow into the Q-junction converges according to a NADH:succinate ratio of 4:1 (Fig. 6.4)."
"A rapidly growing number of studies on various tissues and cells points to the importance of the additive effect of substrate combinations on OXPHOS-capacity (Gnaiger 2009). Convergent electron flow to the Q-junction in the NS-pathway resolves discrepancies between living cells and mitochondria. This additive effect indicates a high downstream excess capacity of respiratory complexes including cytochrome c oxidase (CIV) over Complexes CI and CII."
Ordering complexes is dangerous, should be reconsidered as drugs.
My selection was toxic, read the rest.
- MitoPedia: MiP concepts - Bioblast
- Cellular respiration - Wikipedia
- electron transport chain substrates inhibitors | Google Images (for the experiments)
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