Chapter 15, Problem 1E

How does a developing fetus get oxygen in the womb?

Interpretation Introduction

To determine:

Describe how a fetus gets oxygen in the womb.

Answer to Problem 1E

Solution:

Oxygen is carried in the mother’s blood by hemoglobin and the oxygen is released in the placenta. The hemoglobin in the fetus then binds to the oxygen that was released by the mother’s blood and the fetus carries that oxygen in its own circulatory system.

Explanation of Solution

Oxygen is carried through the blood by hemoglobin and uses the following reaction:

  $Hb+O_2\rightleftharpoons Hb{O}_2$

The blood of the mother comes very close to the blood of the fetus, but the two bloods do not actually mix. The hemoglobin from the mother carries the oxygen to the placenta where the oxygen is then released. The oxygen then binds to the hemoglobin of the fetus by the following reaction:

  $HbF+O_2\rightleftharpoons HbF{O}_2$

The equilibrium constant of the fetus’s hemoglobin reaction shown is much larger than the hemoglobin reaction of the mother’s. Therefore, the equilibrium of the second reaction will fall heavily to the right, which suggests that the fetus’s hemoglobin is much better at binding to oxygen than the mother’s hemoglobin.

Conclusion

The fetus gets oxygen from the mother’s hemoglobin which releases the oxygen in the placenta and the fetus’s hemoglobin quickly binds to the oxygen.