【正确答案】Oxygen dissociation curve: The graph of the relationship between the partial pressure of oxygen and the degree of hemoglobin saturation with oxygen, which has a characteristic sigmoid shape. [2`] Influencing factors: pH value, PCO2, temperature and 2,3-diphosphoglycerate (2,3-DPG). [4`] Increase of [H+], PCO2, temperature and 2,3- DPG will induce the curve right shift and more O2 release from Hb for tissue use [2`] while decrease of mentioned–above factors will trigger the curve left shift and more O2 combination with Hb [2`].