because the nucleus is surrounded by a nuclear envelope - a
double membrane.
since it has 2 membranes it is twice as thick as a single plasma
membrane
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The plasma membrane.
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A cell membrane is also known as a plasma membrane or cytoplasmic membrane. The cell membrane separates the interior of a cell from its outside environment. The main function of a cell membrane is to protect the cell from its surroundings.
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plasma membrane
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The plasma membrane is referred to as a biological membrane or bio-membrane.
Briefly, the plasma membrane may also be generally referred to as cell membrane.