4. The Nobel Prize in Physiology or Medicine 2019 was awarded jointly to William G. Kaelin Jr, Sir Peter J. Ratcliffe and Gregg L. Semenza "for their discoveries of how cells sense and adapt to oxygen availability."When oxygen is limited, hypoxic stress triggers the expression of hypoxia inducible factor (HIF) protein in mammalian tissues. Briefly describe the function of HIF-1 and how it affects the rate of glycolysis under hypoxia.