Active and Passive Transport

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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 biological process of maintaining a stable internal environment within a cell or organism to ensure optimal functioning.

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Example: This diagram shows how red blood cells transport oxygen from the lungs to body cells, a key process for maintaining a stable internal environment (homeostasis).

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Cell Membrane Noun

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[sel mem-breyn]

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Cell Membrane

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The semipermeable barrier separating a cell's interior from the outside, controlling the passage of substances into and out of it.

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Example: This image shows the cell membrane using energy (ATP) to actively transport molecules from an area of low concentration to an area of high concentration.

Front

Selectively Permeable Adjective

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[suh-lek-tiv-lee pur-mee-uh-buhl]

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Selectively Permeable

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A property of biological membranes that allows only certain molecules or ions to pass through, regulating cellular transport.

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Example: A selectively permeable membrane acts like a filter, allowing small water molecules to pass through but blocking larger solute particles.

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Phospholipid Bilayer Noun

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

Back

Phospholipid Bilayer

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The fundamental structure of a cell membrane, composed of two layers of phospholipid molecules with hydrophobic tails and hydrophilic heads.

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Example: A cell membrane is a phospholipid bilayer, with water-loving (hydrophilic) heads facing outward and water-fearing (hydrophobic) tails facing inward, controlling what enters and leaves.

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Hydrophobic Adjective

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[hahy-druh-foh-bik]

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Hydrophobic

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The physical property of a nonpolar molecule that is repelled from a mass of water, making it insoluble.

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Example: This diagram shows how hydrophobic ("water-fearing") tails of molecules cluster together to avoid water, a key principle for how cell membranes form.

Front

Hydrophilic Adjective

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[hahy-druh-fil-ik]

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Hydrophilic

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The physical property of a polar molecule that is attracted to and tends to be dissolved by water.

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Example: This diagram shows a cell membrane, where the round 'hydrophilic heads' are water-loving and face the watery areas inside and outside the cell.

Front

Passive Transport Noun

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[pas-iv trans-port]

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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 how molecules naturally move from an area of high concentration (outside the cell) to an area of low concentration (inside the cell) over time.

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Active Transport Noun

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[ak-tiv trans-port]

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Active Transport

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The movement of substances across a cell membrane against a concentration gradient, requiring the expenditure of cellular energy.

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Example: This diagram shows a protein pump using energy (ATP) to move molecules across a cell membrane from an area of low concentration to high concentration.

Front

Concentration Gradient Noun

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[kon-sen-trey-shuhn grey-dee-uhnt]

Back

Concentration Gradient

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The gradual difference in the concentration of a dissolved substance in a solution between two regions.

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Example: This image shows a concentration gradient, where there is a high concentration of particles on one side and a low concentration on the other.

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Equilibrium Noun

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[ee-kwuh-lib-ree-uhm]

Back

Equilibrium

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The state where the concentration of a substance is uniform throughout a space, resulting in no net molecular movement.

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Example: The image shows a solution where particles (solute) are spread out evenly in a liquid (solvent), representing a balanced state called equilibrium.