1. D.6: Transport of respiratory gases

2. Hemoglobin recap…
What can you tell me about….

3. Oxygen dissociation curves
These curves show the affinity hemoglobin has for oxygen.
The degree to which oxygen binds to hemoglobin depends on the partial pressure of oxygen in the blood (pO2).
Under normal cell conditions, there is a narrow range of oxygen partial pressure. When pO2 is low (e.g. muscles during exercise) O2 dissociates from hemoglobin. At high pO2 (e.g. in the lungs), the hemoglobin becomes saturated with O2.

4. http://highered. mheducation
You do not need to know the pressure changes, but this animation may help your understanding of why O2/CO2 move in/out of the blood.

5. CO2 in the blood Form of transport Arterial mmol-1 blood
Venous mmol-1 blood
Rest
Exercise
Dissolved CO2
0.68
0.78
1.32
Bicarbonate ion
13.52
14.51
14.66
CO2 bound to protein
0.3
0.24
Total CO2 in plasma
14.50
15.59
16.22
pH of blood
7.4
7.37
7.14
Use the data in the table to answer these questions:
Calculate the % of CO2 found as bicarbonate ions in the plasma of venous blood at rest.
Compare the changes in total CO2 in the three forms between venous blood at rest and venous blood during exercise

6. Hydrogen carbonate ions
Carbon dioxide is converted into Hydrogen carbonate ions.
Advantages: more soluble, less toxic
Occurs within RBC, catalyzed by the enzyme carbonic anhydrase.
The reaction is reversible.

7. The Bohr shift
Higher metabolic activity results in more CO2 being released into the blood which in turn lowers the pH.
This increased acidity changes the shape of the oxygen saturation curve, the hemoglobin has a lower affinity for oxygen.
The Bohr shift ensures that respiring tissues have enough oxygen when their need for oxygen is the greatest.

8. Effect of CO2 on ventilation rate
Chemoreceptors in the medulla, the aorta and the carotid artery are able to detect a change in blood carbon dioxide.
High levels of carbon dioxide result in an increase in ventilation to prevent CO2 from building up. Normal range of blood pH = 7.35 – 7.45
As a result, hyperventilation occurs in response to exercise.
*Hyperventilation: rapid, deep breathing*
There are two sets of nerves from the medulla oblongata to the lungs, intercostal nerves (stimulating the intercostal muscles of the thorax) and the phrenic nerves stimulating the diaphragm.
Stretch receptors in the walls of the chest and lungs indicate when it is time to exhale.

9. Fetal V’s Adult hemoglobin
Fetal hemoglobin has a higher affinity for oxygen at all partial pressures to ensure that O2 is transferred to the fetus from the maternal blood across the placenta.
It takes approximately 6 months for fetal hemoglobin to be replaced by adult hemoglobin.

10. Smoking