A 21-year-old man is brought to the ER after being found unconscious. He is gasping, and respirations are 24/min. There is evidence that he has vomited recently. Two capsules containing potassium cyanide are found in his shirt pocket. Blood lactate concentration is 3.3 mEq/L (normal = 0.8 ± 0.4 mEq/L). Which of the following processes is most likely inhibited in this patient?
A) conversion of pyruvate to alanine
B) glycolysis
C) mitochondrial electron transport
D) mobilization of fatty acids from adipose tissue
E) release of insulin from pancreas

Question

Quizplus · Accepted Answer

Cyanide inhibits the mitochondrial electron transport chain, specifically by binding to cytochrome c oxidase, leading to impaired oxidative phosphorylation and increased anaerobic metabolism, which results in elevated lactate levels.  Cyanide is a poison that acts by inhibiting electron flow through complex IV of the oxidative phosphorylation machinery. This prevents further mitochondrial electron transport leading to rapid decline in ATP synthesis capacity and ultimately cellular death.

A 21-Year-Old Man Is Brought to the ER After Being