MCAT Content / Plasma Membrane / General Function In Cell Containment

General function in cell containment

Topic: Plasma Membrane

The plasma membrane separates the inside of the cell from its outside environment.

Both prokaryotic and eukaryotic cells have a plasma membrane, a double layer of phospholipids, with proteins and cholesterol that separates the cell interior from the outside environment and it controls what can enter and exit the cell. Unlike the cell wall, it is not rigid and is flexible. Organelles within the cell are also surrounded by a cell membrane to contain their contents and prevent exposure to conditions in and outside of the cell. For example, the nucleus and endoplasmic reticulum are membrane-bound organelles

Practice Questions

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Key Points

• Prokaryotic and eukaryotic cells both have a plasma membrane, which acts as a barrier between the cell’s interior and it’s exterior environment.

Key Terms

plasma membrane: the semipermeable barrier that surrounds the cytoplasm (inside contents) of a cell

prokaryotic: a unicellular organism that lacks a membrane-bound nucleus, mitochondria

eukaryotic: organisms whose cells have a nucleus and organelles enclosed within membranes

phospholipids: a major component of cell membranes consisting of two hydrophobic fatty acid tails and a hydrophilic head consisting of a phosphate group

organelle: a small specialised structure in the cell

nucleus: centre of the cell containing chromosomes

endoplasmic reticulum: a folded organelle covered in ribosomes used for protein synthesis

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