fumarate(in) + succinate(out) => fumarate(out) + succinate(in)
fumarate(in) + succinate(out) => fumarate(out) + succinate(in)
fumarate(in) + succinate(out) => fumarate(out) + succinate(in)
fumarate(in) + succinate(out) => fumarate(out) + succinate(in)