Steps 3 and 4 (isocitrate to alpha-ketoglutarate and alpha-ketoglutarate to succinyl coenzyme A).
Step 5 (succinyl coenzyme A to succinate).
Steps 3 (isocitrate to alpha-ketoglutarate; NADH), 4 (alpha-ketoglutarate to succinyl coenzyme A; NADH), 6 (succinate to malate; FADH2), and 8 (malate to oxaloacetate; NADH).
The anion that results from deprotonation of tyrosine is resonance-stabilised, but the anion that results from deprotonation of serine is not. The tyrosine anion is more stable compared to the serine anion and therefore the tyrosine anion forms more readily.