Cyanide taken up by child. First one to be affected in Kreb's cycle is?

Cyanide inhibits complex IV of ETC. So, if ETC is inhibited and NADH accumulates. If NADH accumulates, it means NAD depleted. So, TCA is affected because each TCA cycle requires 3 NAD (for Isocitrate Dehydrogenase, alpha-ketoglutarate dehydrogenase and Malate Dehydrogenase). Extra information: Cyanide poisoning: Cyanide is probably the most potent inhibitor of ETC (Complex IV). It binds to Fe3+ of cytochrome oxidase blocking mitochondrial respiration leading to cell death. Cyanide poisoning causes death due to tissue asphyxia (mostly of the central nervous system).