Question

1) Describe how the following change during hyperventilation:

a. PO2

b. PCO2

c. pH

2) Explain how erythrocytes contribute (including the names of proteins involved) to the transport of:

a. oxygen

b. carbon dioxide

3) Regarding a leftward shift in the oxygen saturation curve:

a. does this occur in pulmonary or systemic capillaries?

b. does hemoglobin oxygen binding affinity increase or decrease? c. into where does chloride diffuse?

d. into where does bicarbonate diffuse?

e. does carbon dioxide attach to or detach from hemoglobin?

f. do hydrogen ions attach to or detach from hemoglobin?

4) Explain why a drop in PO2 from 100 mmHg to 80 mmHg does not require ventilation to increase to compensate.

Answer 1

1. Hyper ventilation is the sustained and abnormal increase in breathing. During hyperventilation the rate of carbondioxide from the blood is increased. As the partial pressure of carbon dioxide in the blood decreases, respiratory alkalosis, characterized by decreased acidity or increased alkanity of the blood, ensues. This alkalosis causes constriction of the small blood vessels that supply the brain. Because of the lowered arterial PCO2 and increased pH of the blood, the average PO2 is decreased.

2. Erythrocyte consists of the metalloprotein, hemoglobin. Hemoglobin consists of the heme part which is the iron portion and the globin portion. It is the heme part that binds with oxygen and helps in carrying it to the various parts of the body. It carries four oxygen molecules at a time. It forms oxyhemoglobin which is a reversible process

Carbondioxide reversibly attaches the hemoglobin, amino portion forming carbaminohemoglobin.

3. Left ward shift of the oxygen saturation curve occurs when the oxgen affinity is increased in the cells. THis mostly occurs in the lungs where there is always increased affinity to oxygen. Leftward shift takes place in pulmonary capillaries.

The hemoglobin oxygen binding affinity increases.

In the lungs because of higher concentration of bicarbonate in the erythrocytes than in the surrounding blood plasma, some of the bicarbonate will leave the erythrocyte and move down its concentration gradient in to the plasma and at the same time chloride ions will leave the plasma and enters in to the cells to maintain the concentration gradient.

At the the pulmonary capillaries, the chemical reaction that produced bicarbonate is reversed and carbondioxide and water are the products. The bicarbonate in the plsama re-enters the erythrocytes in exchange for chloride ions. Hydrogen ions and bicarbonate ions join to form carbonic acid, which is converted into carbondioxide and water by carbonic anhydrase. Carbondioxide diffuses out of the erythrocytes and in to te plasma, where it can further diffuse across the respiratory membrane in to the alveoli to be exhaled during pulmonary ventilation.

4. A drop in the blood oxygen saturation below 80 mmHg will be compensated by the body automatically by increasing the blood flow to the brain and muscles inorder to mainatin a normal oxygen supply to them for their proper functioning.