Questions and Answers
What is the direction of diffusion in a biological system?
What is the term for the amount of gas diffusing per unit area of membrane per unit time?
What determines the diffusion coefficient of a gas?
What is the result of diffusion in a biological system?
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What is the equation that describes the process of diffusion?
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What is the role of energy in the process of diffusion?
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What is the concentration gradient in a well-mixed system?
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What happens to the concentration gradient over time in a biological system?
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What is a necessary condition for biological gas exchange systems?
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What is the effect of increasing the concentration gradient across the gas-exchanging surface?
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What is the effect of increasing the surface area of the gas-exchanging surface?
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Why do single-celled organisms not require specialized gas exchange surfaces?
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What is the relationship between the volume of a unicellular organism and its gas exchange needs?
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What happens to the surface area to volume ratio of an organism as it increases in size?
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What is the formula for the amount of gas diffusing per unit time?
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Why do larger organisms require specialized gas exchange surfaces?
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Study Notes
Diffusion and Surface Area
- Diffusion occurs down a concentration gradient, with gas molecules moving from high to low concentration.
- It is a passive process, requiring no energy, and follows Fick's Law.
- Fick's Law states that the flux (J) is equal to the diffusion coefficient (D) multiplied by the concentration gradient (dφ/dx) across the membrane.
Factors Affecting Diffusion
- The diffusion coefficient (D) varies depending on the gas molecule size and membrane properties (viscosity, temperature, and hydrophobicity).
- The concentration gradient (dφ/dx) affects the rate of diffusion, with higher gradients resulting in faster diffusion.
- The thickness of the gas-exchanging surface also affects the rate of diffusion, with thinner surfaces allowing for faster diffusion.
Importance of Surface Area
- An increase in the available surface area increases the amount of gas that can diffuse in a given time.
- The amount of gas diffusing per unit time (dq/dt) is the product of the flux (J) and the surface area (A).
- Single-celled organisms have a high surface area to volume ratio, making their cell membrane adequate for gas exchange needs.
- As an organism increases in size, its surface area becomes inadequate for its gas-exchange needs, requiring specialized gas exchange surfaces.
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Description
Learn about the process of diffusion, the exchange of gases, and how it occurs down a concentration gradient. Understand the concept of passive transport and Fick's Law.