Question

Why RBC is not having nucleus

Answer 1

It allows the red blood cell to contain more haemoglobin (and, therefore, carry more oxygen molecules). It also allows the cell to have its distinctive bi-concave shape which aids diffusion - this shape would not be possible if the cell had a nucleus in the way.

Answer 2

Since, RBC cells flow in the passage with a applied force and they need only oxygen, I.e. they have no matter of their own like nerves or others, there is no nucleus.

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