In the presence of saturating amounts of oxaloacetate, the activity of citrate synthase from pig heart tissue shows a sigmoid dependence on the concentration of acetyl-coa, as shown in the graph below. when succinyl-coa is added, the curve shifts to the right and the sigmoid dependence is more pronounced. on the basis of these observations, suggest how succinyl-coa regulates the activity of citrate synthase. why is succinyl-coa an appropriate signal for regulation of the citric acid cycle? how does the regulation of citrate synthase control the rate of cellular respiration in pig heart tissue?