Question

Mammalian RBCs are
(a)Biconcave,circular,non-nucleated.
(b)Biconcave,nucleated.
(c)Oval,nucleated
(d)None of the above

Answer 1

Hint: Red Blood Cells(RBCs) or Erythrocytes are the most abundant of all the cells in the blood. A healthy adult has, on an average, 5 million to 5.5 millions of RBCs mm-3 of blood. These cells are formed in bone marrow in adults.

Complete answer:
Red blood cells are an important element of blood. The job of these cells is to transport oxygen to the body’s tissues. The cytoplasm of these cells contains a protein called haemoglobin.
Haemoglobin is an iron-containing molecule that has an affinity for oxygen. The oxygen binds to this protein and is transported to other body parts. This protein is responsible for the red colour of the blood.
RBCs are biconcave disc-shaped which maximises the cell membrane for the diffusion of oxygen. The shape also helps in easy movement of cells through the blood vessels.
RBCs are enucleated i.e. they lack nucleus so that a large amount of haemoglobin can be accommodated in it.

Additional information:
The other cells present in Blood are WBCs and Platelets.
White blood cells(WBCs) or leucocytes are colourless due to lack of haemoglobin. These cells have nuclei, unlike RBCs.These cells are involved in protecting the body against infectious diseases and other foreign particles.
Platelets or Thrombocytes are formed from bone marrow. These cells are involved in clotting or coagulation of blood.

So, the correct answer is ‘Biconcave, circular, non-nucleated’.

Note: Not all mammals have circular RBCs. RBCs of camels are oval in shape. This shape helps them to survive osmotic stress and extreme dehydrating conditions. But all mammals have enucleated RBCs without any exceptions.