What is the minimum required haemoglobin?
A) 12gm/dl
B) 9.5gm/dl
C) 18gm/dl
D) 10gm/dl

Hint: Haemoglobin is known to be the iron-containing protein that is present in red blood cells which helps in the transport of oxygen to different tissues and organs in almost all vertebrates and sometimes to the tissues of some invertebrates.

Complete answer:
In humans, haemoglobin is known to take up about 96 percent of the dry content of red blood cells. Apart from oxygen haemoglobin also plays an important role in the transportation of other gases such as carbon dioxide as well as nitric oxides. The minimum haemoglobin that must be present per 100ml of blood is 12gm/dl that makes the process of transportation of oxygen to different parts of the body easier.

In humans, haemoglobin exists as a tetramer where each monomer binds to a molecule of oxygen separately. When oxygen binds to one monomer the conformation of haemoglobin changes from the tensed (T) state to the relaxed (R) state. This shift in turn allows more oxygen to bind to the other monomers of the molecule, a property known as cooperative binding and finally results in saturation of the haemoglobin. As a result of this type of binding the binding curve of haemoglobin is sigmoidal in contrast to the normal hyperbolic curve.

Therefore the correct answer is option (A) i.e, 12gm/dl.

Note: Haemoglobin is thus a very important component of the body and any deficiency in the levels of haemoglobin can cause serious diseases such as anaemia that can also lead to hypoxia. Haemoglobin deficiency can be due to genetic defects or other factors such as nutritional deficiency, blood loss, bone marrow problems, etc.