Question

When carbon dioxide is unloaded form the red blood cell during external respiration, which process must occur?

1. oxygen leaves hemoglobin to go to the alveolus

2. carbon dioxide combines with water to form carbonic acid

3. bicarbonate leaves the red blood cell in exchange for a chloride ion

4. carbon dioxide enters the red blood cell and bind to hemoglobin

5. hemoglobin buffers the cell by carrying h+

Answer 1

Option 5-Hemoglobin Buffers the cell by Carrying H+.

External respiration occurs in the lungs( oxygen diffuses -----blood and carbon dioxide diffuses --- alveolar air)

Internal respiration occurs in the metabolizing tissues(O2 diffuses out of the blood and CO2 diffuses out of the cells.

CO2 in the tissues diffues into Blood,they are Transported to Lung Alveoli by-

1.dissolution directly into the blood

2. binding to hemoglobin

3.bicarbonate ion

At Lung,

HCO3- + H+--------------------H2CO3------------H2O + CO2

HbCO2--------------------------Hb + CO2

All the CO2 unloads from the RBC and Diffuses into Lung.

Here hemoglobin buffers the cell by carrying h+.(H+ + HbO2-----------------------HHb + O2)