Question

When the antibiotic valinomycin is added to actively respiring mitochondria, several things happen: the yield of ATP decreases, the rate of O2 consumption increases, heat is released, and the pH gradient across the inner mitochondrial membrane increases. Explain these observations by listing the causal order of events that occur beginning with the addition of valinomycin to the respiring mitochondria and ending with the release of heat. Some events listed do not occur and should not be placed.

Answer 1

Valinomycin is an uncoupler. Therefore its hydrophobic acidic properties made it to diffuse through the mitochondrial membrane releasing protons, disrupts the inner membrane potential of protons and the electrochemical gradient. Thus increased H+ gradient.

As it combines with K+ in the cystosol, it form a lipid solube complex which can not pass through the mitochondrial membrane.Therefore the retained K+ in the cystosol, neutralize the electrical charge inside the cystosol, impeding the PMF, and therefore slow down the ATPase synthesis with time, which corresponding increase in H_ gradient However the electron transport to oxygen is unaffected, therefore electron transport chains continues, oxygen consumption also increase, with liberation of heat energy.

Step-by-step explanation: