Which state is haemoglobin in when it has released oxygen to tissues?

Which state is haemoglobin in when it has released oxygen to tissues?

• A. Oxyhaemoglobin
• B. Carbaminohaemoglobin
• C. Carboxyhaemoglobin
• D. Deoxyhaemoglobin

Answer: (D)

When oxygen is released to tissues, haemoglobin is in the deoxyhaemoglobin form. Hemoglobin picks up oxygen in the lungs to become oxyhaemoglobin, then releases that oxygen where it’s needed in tissues with lower oxygen tension. After releasing O2, the molecule is in its deoxygenated state (deoxyhaemoglobin), ready to pick up carbon dioxide and return to the lungs. The other forms described—carbaminohaemoglobin (CO2 bound to haemoglobin) and carboxyhaemoglobin (CO bound to haemoglobin)—occur in different conditions and aren’t the form Hb is in after delivering oxygen.

When oxygen is released to tissues, haemoglobin is in the deoxyhaemoglobin form. Hemoglobin picks up oxygen in the lungs to become oxyhaemoglobin, then releases that oxygen where it’s needed in tissues with lower oxygen tension. After releasing O2, the molecule is in its deoxygenated state (deoxyhaemoglobin), ready to pick up carbon dioxide and return to the lungs. The other forms described—carbaminohaemoglobin (CO2 bound to haemoglobin) and carboxyhaemoglobin (CO bound to haemoglobin)—occur in different conditions and aren’t the form Hb is in after delivering oxygen.