<prompt> Oxygen delivery to tissues in body is cut in half by 50 reduction in?HaemoglobinOxygen saturationPartial pressure of oxygenArterial content of oxygen  <response>: Ans. a Haemoglobin. Ref. Ganong, Physiology, 21st ed., 671OXYGEN DISSOCIATION CURVE Normal oxygen uptake is 250 mlmin 1 gm of Hb carries 1.34 ml of oxygen O2 dissociation curve is sigmoid in shape The O2-binding curve for myoglobin is hyperbolic, but for hemoglobin it is sigmoidal, because of cooperative interactions in the tetramer Binding of oxygen to one molecule of hemoglobin increases the affinity for other oxygen molecules. Bohr effect: Alkalosis shifts O2 dissociation curve to left and acidosis to right. Halden effect: Deoxygenated blood has more CO2 content at a given pCO2. Shift of O2 dissociation curve to leftO2 releaseShift of O2 dissociation curve to rightIncreased O2 binding to Hb1AlkalosisAcidosis2Decreased temperatureIncreased temperature3Increased pH Bohrs effectDecreased pH4Deoxygenated HbHigh altitude5Hb FHypoxia6Abnormal HbsVasoconstriction7Decreased PCO2Increased PCO28Decreased 2-3-DPG exercise, bank bloodIncreased 2-3-DPG9Increased PO2 10Hypophosphatemia 11Methemoglobinaemia 