Molecular Diffusion
Molecular Diffusion - Related Videos
03:48
Behavior of Gas Molecules: Molecular Diffusion, Mean Free Path, and Effusion
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2020
Although gaseous molecules travel at tremendous speeds (hundreds of meters per second), they collide with other gaseous molecules and travel in many different directions before reaching the desired target. At room temperature, a gaseous molecule will experience billions of collisions per second. The mean free path is the average distance a molecule travels between collisions. The mean free path increases with decreasing pressure; in general, the mean free path for a gaseous molecule will be...
12:19
Mapping Molecular Diffusion in the Plasma Membrane by Multiple-Target Tracing (MTT)
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Cited by 4 •
2012
Multiple-Target Tracing is a homemade algorithm developed for tracking individually labeled molecules within the plasma membrane of living cells. Efficiently detecting, estimating and tracing molecules over time at high-density provide a user-friendly, comprehensive tool to investigate nanoscale membrane dynamics.
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Diffusion and Osmosis - Concepts
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2019
Cell Membranes and Diffusion In order to function, cells are required to move materials in and out of their cytoplasm via their cell membranes. These membranes are semipermeable, meaning that certain molecules are allowed to pass through, but not others. This movement of molecules is mediated by the phospholipid bilayer and its embedded proteins, some of which act as transport channels for molecules that otherwise would not be able to pass through the membrane, such as ions and carbohydrates.
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Diffusion and Osmosis - Student Protocol
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2019
Diffusion in Agar ExpandNOTE: In this exercise, you will be given agar containing an indicator chemical called phenolphthalein. When phenolphthalein is exposed to the normal alkaline conditions in the agar, it will look pink. But when it is exposed to neutral or acidic conditions, it changes from pink to clear. You will make different size and shaped agar cubes as a model for cells to study the impact of cell size and shape on diffusion rate. To make the first set of cells, measure out and cut...
05:26
Dialysis: Diffusion Based Separation
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2023
Dialysis is a common technique used in biochemistry for separating molecules based on diffusion. In this procedure, a semipermeable membrane allows the movement of certain molecules based on size. This method can be applied to the removal of buffer, known as desalting, or exchanging buffer molecules or ions from a protein solution. This video covers the principles of dialysis along with a general procedure. Several applications of dialysis are reviewed, including the removal of gradient...
FAQs
Concentration gradients determine the direction of net molecular movement, while random thermal motion produces the individual movements behind that pattern. Molecules do not travel in a single organized stream; the measurable result emerges from many random movements. As concentrations become more similar, the net movement decreases, helping explain how diffusion contributes to balance within biological systems.
Temperature, molecular size, travel distance, and the surrounding medium alter how quickly diffusion proceeds. Higher temperature changes thermal motion, whereas larger molecules may move less readily. A longer path reduces the speed of redistribution, and the medium can either facilitate or hinder movement. These variables must be considered when comparing diffusion in cells, tissues, or experimental models.
Membrane properties determine whether a concentration difference can produce movement across a cell boundary. A molecule must encounter a membrane that is sufficiently permeable for diffusion to occur through it; otherwise, the gradient may remain separated across the barrier. This makes membrane permeability a key variable when interpreting transport, homeostasis, and exchange between cellular compartments.
A molecule crossing a short distance can redistribute more readily than one traveling through a longer path, so tissue geometry affects exchange. This principle helps connect molecular-scale motion with oxygen and carbon dioxide movement in biological tissues. It also explains why diffusion-based models should represent the relevant separation between source and destination.
Researchers can examine how concentration differences change across fluids, membranes, cells, or tissues while considering temperature, molecular size, distance, and medium properties. The resulting patterns help evaluate transport and redistribution rather than treating movement as independent of context. Such experiments and models can clarify cellular homeostasis, nutrient distribution, waste removal, and signaling transport.
Exchange of oxygen and carbon dioxide, nutrient distribution, waste removal, and signaling molecule transport all depend on diffusion under suitable concentration and membrane conditions. If those conditions change, the rate of redistribution can change as well. Consequently, diffusion is central to interpreting how cells maintain homeostasis and how substances move through biological systems.