Obtaining and Removing Materials

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Homeostasis Noun

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[hoh-mee-oh-stay-sis]

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Homeostasis

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The maintenance of a stable, constant internal environment within a cell or organism despite external changes.

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Example: This image uses a balanced scale as a simple metaphor for homeostasis, representing the body's ability to maintain a stable, balanced internal state.

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Cell Membrane Noun

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[sel mem-brayn]

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Cell Membrane

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The semipermeable barrier surrounding the cytoplasm of a cell, controlling the passage of substances into and out of it.

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Example: This diagram shows the cell membrane is a barrier with special proteins, like channels, that control what moves into and out of the cell.

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Phospholipid Bilayer Noun

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[fos-foh-lip-id by-lay-er]

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Phospholipid Bilayer

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The fundamental double-layered structure of a cell membrane, composed of phospholipid molecules with hydrophilic heads and hydrophobic tails.

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Example: This diagram shows the phospholipid bilayer is made of two layers, with water-loving (hydrophilic) heads facing out and water-fearing (hydrophobic) tails facing in.

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Phospholipid Noun

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[fos-foh-lip-id]

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Phospholipid

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A lipid molecule containing a hydrophilic phosphate head and two hydrophobic fatty acid tails, forming the basis of cell membranes.

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Example: This image shows a phospholipid as one component of a cell membrane, where many phospholipids form a double layer called a bilayer.

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Hydrophobic Adjective

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[hy-droh-foh-bik]

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Hydrophobic

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The physical property of a molecule that is repelled from a mass of water, meaning it does not mix.

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Example: This image shows water droplets beading up on a leaf's waxy surface. Because the surface is hydrophobic, it repels the water, preventing it from spreading.

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Selective Permeability Noun

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[suh-lek-tiv per-mee-uh-bil-i-tee]

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Selective Permeability

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The characteristic of a cell membrane that allows certain molecules or ions to pass through it while restricting others.

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Example: This image shows a selectively permeable membrane that acts like a filter, allowing small particles to pass through its pores while blocking larger particles.

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Transport Proteins Noun

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[trans-port proh-teenz]

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Transport Proteins

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Membrane proteins that facilitate the movement of substances across the cell membrane, either passively or by using energy.

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Example: This image shows how transport proteins, embedded in the cell's plasma membrane, act like gates to move specific molecules from outside to inside the cell.

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Glycoproteins Noun

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[gly-koh-proh-teenz]

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Glycoproteins

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Proteins that have carbohydrate chains attached to them, often serving as cell-surface receptors and for cell-to-cell recognition.

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Example: This image shows a glycoprotein, which is a protein with a sugar chain attached, located on the outer surface of a cell's membrane.

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Glycolipids Noun

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[gly-koh-lip-ids]

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Glycolipids

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Lipids with a carbohydrate attached by a glycosidic bond, which function to maintain membrane stability and facilitate cellular recognition.

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Example: A glycolipid is made of a sugar chain ('glyco') attached to a lipid. This diagram shows it as part of a cell's lipid membrane.

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Cholesterol Noun

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[kuh-les-tuh-rawl]

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Cholesterol

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A lipid molecule in animal cell membranes that modulates membrane fluidity, stability, and permeability over various temperatures.

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Example: This diagram shows that cholesterol is a molecule found inside the cell membrane, where it helps provide structure and stability.