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What is a cell membrane?

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Quick Answer

A cell membrane is a thin layer that acts as a barrier that separates an individual cell or a cellular compartment from other surrounding structures. This dynamic layer plays an essential part in the transport of ions and nutrients.

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What is a cell membrane?
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A cell membrane is a complex structure made of proteins, phospholipids, cholesterol, carbohydrates and several other compounds, all of which are held in place by non-covalent forces. Each cell membrane component serves one or more essential purposes. For example, the proteins act as pumps, gates or receptors, and the lipids create hydrophobic barriers that keep aqueous compartments separate. Cholesterol increases the strength and flexibility of the membrane while also making it less permeable to aqueous compounds.

The transport across cell membranes is an essential cell function, and it depends on the layered membrane structure and the nature of the molecule to be transported. Some molecules, such as oxygen and glucose, are transported through the membrane without requiring any energy, but ions, such as sodium and potassium, are only transported actively, which means that energy is required. The cell membrane is also capable of expelling part of its contents outside through a process called exocytosis or enveloping external molecules through endocytosis. Other functions of the cell membrane include providing shape to the cell by anchoring the cytoskeleton, maintaining the cell potential and sending molecular signals to other cells.

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Related Questions

  • Q:

    What is the difference between the cell wall and the cell membrane?

    A:

    Unlike the cell membrane, the cell wall is not common to all types of cells. A protective layer that surrounds the cell membrane, one of its main functions is to prevent over-expansion of a cell.

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  • Q:

    What would happen if there was no cell membrane?

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    The cell membrane is essential to the life of the cell and without it, the cell dies. If all the cells in an organism suddenly die, the organism itself dies as well.

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  • Q:

    What is an analogy for the cell membrane?

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    The cell membrane is a lot like a wall or fence surrounding a city that keeps everything that is dangerous or harmful out, but lets in and out certain materials that are vital for the cell to survive. The chemicals on the cell membrane recognize which materials should be able to push through it, much like a gate in a fence or wall.

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  • Q:

    Why is the cell membrane said to be selectively permeable?

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    The cell membrane is said to be selectively permeable because it lets certain substances pass through while restricting the passage of others. The actual structure of the cell membrane allows free passage or restricts movement of substances across the membrane. Three ways in which the cell membrane controls the movement of substances is simple diffusion, facilitated diffusion and active transport.

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