Talk:Citric acid cycle

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Citric Acid Cycle Diagram[edit]

This diagram is really messy. The molecules could be less bulky looking. (having the molecules not be the stick and ball structure and instead have it be the normal structural formula) Also having backwards arrows on some reactions would help identify which steps are reversible or not.

Geowong (talk) 18:25, 18 March 2017 (UTC)

I agree with Geowong's comments. The diagram is hard to read because of the unfamiliar ball-and-stick representations. Also please remove the reaction of pyruvate carboxylase: having it in the diagram obscures the cyclic nature of the citric acid cycle. JoNo672 (talk) 14:49, 12 April 2018 (UTC)

Succinate dehydrogenase is a member of the electron transport chain as well as the TCA cycle; its substrate is succinate not FADH2[edit]

In summarizing the reducing equivalents provided to the electron transport chain, there is a complication in that succinate dehydrogenase (or rather Complex II) is part of both the TCA cycle and the electron transport chain. It is a little misleading to say 3 NADH and one FADH2 are provided: Yes, FAD is the cofactor in SDH that gets reduced first, but by the same token the NADH dehydrogenase has a flavin (mononucleotide) which accepts the electrons from NADH. The main substrates of the electron transport chain are NADH and succinate, not NADH and FADH2. However it can't be said that the cycle produces succinate, the way it produces NADH. It might be said that one turnover of the cycle supplies the ETC with 3 NADH and one succinate, then go on to explain that oxidation of succinate by SDH constitutes the first step in oxidation of succinate by the ETC, as well as a step in the TCA cycle. Or that might be even more confusing.
An easy way out would be to divorce Complex II from the respiratory chain and consider it only a member of the TCA cycle (albeit membrane bound), especially since there is no energy coupling in this step. Then we could say the TCA cycle provides 3 NADH and one ubiquinol to the electron transfer chain. But the long history of "Complex II of the respiratory chain" would make this problematic. Eaberry (talk) 05:26, 26 April 2018 (UTC)