This lack of a concentration gradient in which there is no net movement of a substance is known as dynamic equilibrium. While diffusion will go forward in the presence of a concentration gradient of a substance, several factors affect the rate of diffusion:. A variation of diffusion is the process of filtration. In filtration, material moves according to its concentration gradient through a membrane; sometimes the rate of diffusion is enhanced by pressure, causing the substances to filter more rapidly.
This occurs in the kidney where blood pressure forces large amounts of water and accompanying dissolved substances, or solutes, out of the blood and into the renal tubules. The rate of diffusion in this instance is almost totally dependent on pressure. Learning Objectives Describe diffusion and the factors that affect how materials move across the cell membrane. Key Points Substances diffuse according to their concentration gradient; within a system, different substances in the medium will each diffuse at different rates according to their individual gradients.
After a substance has diffused completely through a space, removing its concentration gradient, molecules will still move around in the space, but there will be no net movement of the number of molecules from one area to another, a state known as dynamic equilibrium.
Several factors affect the rate of diffusion of a solute including the mass of the solute, the temperature of the environment, the solvent density, and the distance traveled. Key Terms diffusion : The passive movement of a solute across a permeable membrane concentration gradient : A concentration gradient is present when a membrane separates two different concentrations of molecules. Diffusion Diffusion is a passive process of transport.
Factors That Affect Diffusion Molecules move constantly in a random manner at a rate that depends on their mass, their environment, and the amount of thermal energy they possess, which in turn is a function of temperature. While diffusion will go forward in the presence of a concentration gradient of a substance, several factors affect the rate of diffusion: Extent of the concentration gradient: The greater the difference in concentration, the more rapid the diffusion.
The closer the distribution of the material gets to equilibrium, the slower the rate of diffusion becomes. For a bacterium , substances diffuse into and out of the bacterial cell across its surface.
For simple multicellular organisms , such as small plants like mosses, substances diffuse into the leaves and roots over their surface. Again, once inside the plant, they don't need to move far. Substances move into and around the moss plants by diffusion and osmosis. Simple organisms take in substances over their body surface. Their needs are determined by their volume.
As organisms increase in size, their surface area does not increase at the same rate as their volume. For example, the surface area to volume ratio of a puppy is several times greater than that of an adult dog.
Suggest why puppies are more at risk of losing body heat than adult dogs. Dogs lose heat over their body surface. Puppies have a larger surface area to volume ratio than adult dogs, so will lose heat more readily. The large sugar molecule moves slower because of its size. The viscosity of the solution affects both but will compound the slowed diffusion that the larger molecule undergoes.
Any factor that speeds up movement of particles through a medium will result in a faster rate of diffusion. She has an interest in astrobiology and manned spaceflight. She has over 10 years of biology research experience in academia. She currently teaches classes in biochemistry, biology, biophysics, astrobiology, as well as high school AP Biology and Chemistry test prep. Characteristics of a Colloid. How Does Diffusion Work? Chemistry Projects for Diffusion in Liquids.
How Does Ink Diffuse in Water? How to Calculate Diffusion Rate. How to Calculate Solubilities. How to Calculate Isotonicity. What Affects the Osmolarity of a Solution? Density Vs. Electrophoresis Process. References Biology LibreTexts: 5.
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