And so red blood cells actually depend entirely on the glucose found inside the blood plasma, as do the brain cells and muscle cells of our body. So all these different types of cells actually get that glucose from the blood uptake that glucose and then use the glucose, break it down in glycolysis to form the ATP. And that's why it's so important that our liver cells and kidney cells can actually properly regulate the levels of glucose in our blood. Now, previously we saw how the energy charge value within the cell, the ratio of ATP to amp can actually be used to regulate the process of glycolysis and gluconeogenesis. So we can use the energy charge of the cell to basically tell us if glycolysis or glucomaogenesis actually predominates. Now, although that's true for liver cells and for kidney cells, because they regulate and maintain glucose levels, they also can use the glucose levels in the blood to basically determine whether glycolysis or gluconeogenesis actually predominate.