Question

As per chemiosmotic coupling hypothesis, in mitochondria, protons accumulate in the

• A. outer membrane
• B. inner membrane
• C. intermembrane space
• D. matrix

Answer 1

Answer: (C)

intermembrane space

Answer 2

Chemiosmotic coupling hypothesis, proposed by Peter Mitchell $(1961$, $66)$ (Nobel Prize in $1978$), is the most widely accepted theory for oxidative phosphorylation. Reduced $NAD$ (i.e., $NADH$), released from Krebs' cycle, when enters in the $ETS$, transports three pairs of $H^+$ across the inner mitochondrial membrane to the intermembrane space. Similarly, $NADH$ from glycolysis and $FADH_2$ from Krebs' cycle also transport pairs of $H^+$ into intermembrane space. Each molecule of $NADH$ released from glycolysis or $FADH^2$ from Krebs' cycle transports two pairs of protons into intermembrane space. This unidirectional flow of protons results in the accumulation of protons in the intermembrane space.