Question

question 26
the mechanism that produces pulmonary ventilation is one that establishes a gas pressure gradient between the
atmosphere and air in the upper respiratory tract.
atmosphere and the alveolar air.
alveolar air and the upper respiratory tract.
none of the above.
question 27
the exit of the bicarbonate ion from the red blood cell is balanced by the inward transport of another negative ion, chloride. this countertransport of negative ions is often called the ____ shift.
bicarbonate
carbonic
chloride
right
question 28
which oxygen - binding protein helps move oxygen out of the blood and into muscle cells?
fetal hemoglobin
myofibril
myoglobin
carbaminohemoglobin

Explanation:

• Question 26: Pulmonary ventilation (breathing) occurs due to a pressure gradient between the atmosphere and the alveolar air. Air moves from an area of higher pressure (atmosphere during inhalation, alveoli during exhalation) to an area of lower pressure. The upper respiratory tract is just a passageway, and the key gradient is between the atmosphere and alveoli.
• Question 27: The chloride shift is the movement of chloride ions ($Cl^-$) into red blood cells to balance the outward movement of bicarbonate ions ($HCO_3^-$). This helps maintain electrical neutrality in the red blood cell.
• Question 28: Myoglobin is an oxygen - binding protein found in muscle cells. It has a higher affinity for oxygen than hemoglobin at low partial pressures of oxygen. So, it helps in the transfer of oxygen from the blood (where hemoglobin releases oxygen at the muscle tissue level) into muscle cells. Fetal hemoglobin is a type of hemoglobin in the fetus. Myofibrils are the contractile elements of muscle cells (made of actin and myosin). Carbaminohemoglobin is hemoglobin bound to carbon dioxide.

Answer:

• Question 26: atmosphere and the alveolar air.
• Question 27: chloride.
• Question 28: myoglobin.