Question

Describe in 3-4 sentences how the hemoglobin (Hb) in red blood cells delivers more oxygen to active cells, than cells at rest. Include, differences in partial pressure, pH, and [carbon dioxide]. (There might be a very small effect of temperature, but you can leave it out because it is a minor contributor in humans.)

Answer 1

Tissues having higher metabolic rate demand more oxygen.

Mostly active tissues, like muscles rapidly use oxygen for production of ATP, thus partial pressure of oxygen is reduced to 20mm Hg. The partial pressure(pp) of O2 inside capillaries is nearly100 mm Hg, the difference in partial pressure becomes high, hence oxygen dissociates from Hb and releases to tissues.

The reverse occurs in case of adipose having low metabolic rates. less oxygen is used by adipose cells, the pp of oxygen remains high, results in less oxygen molecules to dissociate from hemoglobin. The oxygen left in venous blood acts as an oxygen reserve that is used when tissues suddenly demand Hb.

Cells at rest demand less oxygen, there is no or very less requirement of energy , hence less dissociation of oxygen from Hb.

FACTORS AFFECTING DISSSOCIATION
BLOOD TEMPERATURE : increased blood temperature reduces haemoglobin affinity for 02 hence more 02 delivered to warmed-up tissue
BLOOD Ph : lowering of blood pH (making blood more acidic) caused by presence of H+ ions from lactic
acid or carbonic acid reduces affinity Of Hb for 02 and more 02 delivered to acidic sites which are working harder .

CARBON DIOXIDE CONCENTRATION: the higher C02 concentration in tissue the less the affinity of Hb for 02 so the harder the tissue is working, the more 02 is released.

Hemoglobin saturation: During exercise the partial pressure of oxygen in cells drops well below 40 mm Hg. As oxygen levels decline, hemoglobin saturation declines at a higher rate - blood (hemoglobin) 'unloads' lots of oxygen to active cells that require more oxygen to produce energy.

As 02 diffuses from the alveoli into the pulmonary capillary blood, it dissolves in the plasma of the blood.
At normal body temperature about 0.003 ml of 02 will dissolve in 100 ml of blood for every 1 mm Hg of P02
In terms of total oxygen transport, a relatively small percentage of 02 is transported in the form of dissolved 02.

Transport of Oxygen to the tissues there is high [carbon dioxide] this reduces Hb affinity for oxygen so it gives it up Conversely at lungs there is low [carbon dioxide] so the Hb has a greater affinity for
oxygen — so picks up more.

C02 content rises throughout the increase in partial pressure.
02 content rises more steeply until a point at which the Hb is fully saturated. After that, the increase is small because of the small increased amount in solution.

Consequently, the C02 curve is mote linear than the 02Hb dissociation curve.

Graph illustrates the difference between the content in blood of oxygen and carbon dioxide with change in partial pressure.

Right shift of oxygen-Hb dissociation curve. Fetal Hb has higher affinity of O2 than adult Hb then dissociation curve shifted to left.