Carbon dioxide transport Drag each label to the appropriate location on the flowchart.
The Correct Answer and Explanation is :
To accurately answer this, I’ll describe the flowchart for carbon dioxide (CO₂) transport in the blood and explain each step. Here’s how the flowchart might typically look:
Carbon Dioxide Transport Flowchart
- CO₂ diffuses from tissues into blood
↓ - CO₂ enters red blood cells (RBCs)
↓ - CO₂ reacts with water (H₂O) to form carbonic acid (H₂CO₃), catalyzed by carbonic anhydrase
↓ - Carbonic acid dissociates into bicarbonate ions (HCO₃⁻) and hydrogen ions (H⁺)
↓ - Bicarbonate ions leave RBCs and are transported in plasma (chloride shift occurs to maintain ionic balance)
↓ - At the lungs, bicarbonate reenters RBCs
↓ - Bicarbonate ions combine with H⁺ to form carbonic acid, which is converted back into CO₂ and water
↓ - CO₂ diffuses into alveoli and is exhaled
Explanation (300 words)
Carbon dioxide is a byproduct of cellular metabolism and must be transported from tissues to the lungs for exhalation. This process occurs in three main forms: dissolved CO₂ in plasma (7-10%), chemically bound to hemoglobin as carbaminohemoglobin (20-30%), and as bicarbonate ions in plasma (60-70%).
- Diffusion: CO₂ diffuses from metabolically active tissues into the blood due to its concentration gradient.
- Inside RBCs: Most CO₂ enters red blood cells. There, carbonic anhydrase catalyzes its reaction with water to form carbonic acid (H₂CO₃).
- Dissociation: Carbonic acid rapidly dissociates into bicarbonate ions (HCO₃⁻) and hydrogen ions (H⁺). To balance charge, HCO₃⁻ diffuses out of RBCs into the plasma, and chloride ions (Cl⁻) move into the RBCs (chloride shift).
- At the lungs: The reverse occurs. Bicarbonate reenters RBCs, combines with H⁺ to reform H₂CO₃, which is then converted back into CO₂ and H₂O. The CO₂ diffuses into the alveoli and is exhaled.
This dynamic process ensures efficient CO₂ transport, buffering blood pH through bicarbonate, and maintaining homeostasis.