Diffusion and Osmosis

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Homeostasis Noun

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[ho-mee-o-stay-sis]

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Homeostasis

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The maintenance of a relatively stable internal environment necessary for an organism to survive and function correctly.

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Example: This diagram shows how red blood cells maintain homeostasis by using diffusion to pick up oxygen from the lungs and deliver it to body cells.

Front

Selectively Permeable Adjective

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

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Selectively Permeable

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A property of a membrane that allows only certain molecules or ions to pass through it via active or passive transport.

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Example: A selectively permeable membrane acts like a filter, allowing small particles (like water) to pass through its pores while blocking larger particles.

Front

Concentration Gradient Noun

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[kon-sen-tray-shun gray-dee-ent]

Back

Concentration Gradient

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The difference in the concentration of a substance between two areas, which dictates the direction of passive transport.

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Example: The beakers show a gradual change in the concentration of a substance, from high (dark purple liquid) on the left to low (light purple liquid) on the right.

Front

Equilibrium Noun

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[ee-kwuh-lib-ree-um]

Back

Equilibrium

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The state where particle concentration is the same inside and outside a cell, resulting in no net movement across the membrane.

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Example: In a solution at equilibrium, solute particles are spread out evenly among the solvent particles, resulting in a uniform concentration throughout.

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 molecules across a cell membrane from a high to low concentration without requiring the use of energy.

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Example: This diagram shows molecules moving from a high concentration area (extracellular fluid) to a low concentration area (cytoplasm) directly across the cell membrane.

Front

Diffusion Noun

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[di-fyoo-zhun]

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Diffusion

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The passive movement of particles from an area of higher concentration to an area of lower concentration until equilibrium is reached.

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Example: This diagram shows particles moving from an area of high concentration to an area of low concentration across a cell membrane, illustrating the process of diffusion.

Front

Osmosis Noun

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[oz-mo-sis]

Back

Osmosis

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The passive diffusion of water molecules across a selectively permeable membrane from a region of high to low water concentration.

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Example: This diagram shows osmosis by illustrating how red blood cells change shape. Water moves out of the cell in a hypertonic solution, stays balanced in an isotonic solution, and moves into the cell in a hypotonic solution.

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Facilitated Diffusion Noun

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[fuh-sil-i-tay-tid di-fyoo-zhun]

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Facilitated Diffusion

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A type of passive transport that uses a transport protein to help move molecules across the cell membrane.

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Example: Molecules move from a high concentration area to a low concentration area by passing through special carrier proteins embedded in the cell membrane.

Front

Active Transport Noun

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[ak-tiv trans-port]

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Active Transport

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The movement of particles through a cell membrane from a lower to a higher concentration, requiring the use of energy.

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Example: This diagram shows active transport, where a cell uses energy (ATP) to move substances through a protein from a low concentration to a high concentration.

Front

Adenosine Triphosphate (ATP) Noun

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[uh-den-uh-seen try-fos-fayt]

Back

Adenosine Triphosphate (ATP)

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The molecule that provides the chemical energy for active transport and other essential cellular processes.

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Example: This image shows the three parts of an ATP molecule: adenine, a ribose sugar, and a chain of three phosphate groups.