As far as I am aware, all steps in glycolysis are readily reversible except the phosphorylation of glucose, the phosphorylation of fructose6 phosphate, and the phosphorylation of phosphoenolpyruvate to pyruvate. I understand how control of the rate of glycolysis can be achieved through allosteric means (for example glucose 6 phosphate inhibiting hexokinase in muscle cells, phosphofructokinase being under allosteric control of the ATP/AMP ratio in muscle or hormonal control via glucagon in liver), however how is the rate of gluconeogenesis controlled compared with glycolysis? When a cell has a high rate of glycolysis, then as the rate of forwards reaction increases the concentration of substrate for each gluconeogenesis reaction also increases. Thus there must be some way to shut off the gluconeogenesis enzymes.
I would be grateful if someone could explain how the relative rates of glycolysis and gluconeogenesis are controlled, and perhaps if this varies according to the cell type (muscle/liver cells etc).
I was also wondering whether every cell is capable of gluconeogenesis. I was considering putting this on a separate post so that there is only one question per post, but I thought that it is quite a short question so it may be better to put it here.