Plasma membrane is also called lipid bilayer. So would it be right to call it a" membrane bilayer" ? Moreover, please see the question attached . Question Number 80 (last question) in the...

Plasma membrane is also called lipid bilayer.

So would it be right to call it a" membrane bilayer" ?

Moreover, please see the question attached .

Question Number 80 (last question) in the attached image.

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lynn30k eNotes educator| Certified Educator

Short answer, yes--because the membranes surrounding both the cell itself, and various organelles, are two layers ("bi" means two; a bicycle has two wheels), all of these terms are correctly used, and mean the same thing. Each membrane is made of two layers of lipid molecules, with their "tails" toward the interior, and have protein channels that help some molecules enter and exit either the cell or the organelle. 

This may be why you have a question about number 80 on your image. Each time the imaginary line passes through the membrane, you should count it as one time, even though the membrane has two layers. Since the line is going through the cell membrane, that counts as one time. It passes through a mitochondrion, which is surrounded by a membrane; since it enters, then leaves, that is two more membranes the line passes through. It then enters the nucleus, which also is surrounded by a membrane, making the total four times the line goes through a membrane on its way from the outside of a cell, through a mitochondrion, and into the nucleus.

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