Cell Membrane

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Plasma Membrane Noun

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[plaz-muh mem-breyn]

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Plasma Membrane

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The semipermeable barrier surrounding a cell, controlling what enters and leaves; also known as the cell membrane.

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Example: This diagram shows the plasma membrane is a flexible barrier with embedded proteins that control what substances can pass into or out of the cell.

Front

Homeostasis Noun

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[hoh-mee-oh-stey-sis]

Back

Homeostasis

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The tendency of a system, such as a cell, to maintain a stable, balanced internal environment.

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Example: This diagram shows a red blood cell delivering oxygen to body cells, a process that maintains stable oxygen levels, which is an example of homeostasis.

Front

Semipermeable Adjective

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[sem-ee-pur-mee-uh-buhl]

Back

Semipermeable

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A property of a membrane that allows certain substances to pass through but prevents others from passing.

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Example: This diagram shows a semipermeable cell membrane, which acts as a selective barrier, allowing certain molecules like water to pass through into the cell.

Front

Phospholipid Noun

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[fos-foh-lip-id]

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Phospholipid

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A lipid molecule with a hydrophilic head and two hydrophobic tails that is the main component of cell membranes.

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Example: This diagram shows how a phospholipid has a water-loving (hydrophilic) head and a water-fearing (hydrophobic) tail, causing them to form a lipid bilayer.

Front

Hydrophilic Adjective

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[hahy-droh-fil-ik]

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Hydrophilic

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Describes molecules or parts of molecules that are attracted to, and can interact with or dissolve in, water.

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Example: This diagram shows a cell membrane's phospholipid bilayer, where the round 'hydrophilic heads' face outwards because they are attracted to water.

Front

Hydrophobic Adjective

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[hahy-droh-foh-bik]

Back

Hydrophobic

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Describes molecules or parts of molecules that repel or do not mix with water, often being nonpolar.

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Example: This diagram shows that hydrophobic ('water-fearing') tails of molecules cluster together to avoid water, surrounding an oil droplet, a key principle in cell membrane formation.

Front

Phospholipid Bilayer Noun

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[fos-foh-lip-id bahy-ley-er]

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Phospholipid Bilayer

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The double layer of phospholipid molecules that forms the basic structure of a plasma membrane, with tails facing inward.

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Example: This diagram shows the phospholipid bilayer as two layers of molecules, forming the basic structure of the cell membrane, which also contains various proteins.

Front

Fluid Mosaic Model Noun

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[floo-id moh-zey-ik mod-l]

Back

Fluid Mosaic Model

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A model describing the cell membrane as a dynamic structure with proteins embedded in a fluid phospholipid bilayer.

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Example: The cell membrane is a fluid mosaic, with various proteins and carbohydrates embedded or attached to a flexible, double layer of phospholipids.

Front

Passive Transport Noun

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[pas-iv trans-port]

Back

Passive Transport

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The movement of substances across a cell membrane from high to low concentration without requiring cellular energy.

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Example: This image shows molecules moving across a cell membrane over time, from an area of high concentration to an area of low concentration, without using energy.

Front

Diffusion Noun

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[dih-fyoo-zhuhn]

Back

Diffusion

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The passive movement of molecules or particles from an area of higher concentration to an area of lower concentration.

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Example: Carbon dioxide (CO2) molecules move from an area of high concentration to an area of low concentration, passing directly through the cell membrane.