diffusion

Examples of diffusion in the following topics:

• Diffusion

  • Diffusion is the movement of particles from regions of high concentration towards regions of lower concentration.
  • Molecular diffusion, often called simply diffusion, is the thermal motion of all (liquid or gas) particles at temperatures above absolute zero.
  • However, diffusion can still occur in the absence of a concentration gradient.
  • The result of diffusion is a gradual mixing of material.
  • Discuss the process and results of diffusion, identifying factors that affect its rate

• Diffusion

  • Diffusion is a passive process of transport.
  • Materials move within the cell's cytosol by diffusion, and certain materials move through the plasma membrane by diffusion.
  • Diffusion expends no energy.
  • Mass of the molecules diffusing: Heavier molecules move more slowly; therefore, they diffuse more slowly.
  • If the medium is less dense, diffusion increases.

• Molecular Transport Phenomena

  • These include diffusion and osmosis.
  • More massive molecules diffuse more slowly.
  • This type of diffusion is called free diffusion, because there are no barriers inhibiting it.
  • The rate of diffusion is also proportional to the diffusion constant D, which is determined experimentally.
  • Some of the most interesting examples of diffusion occur through barriers that affect the rates of diffusion.

• The Respiratory System and Direct Diffusion

  • As animal size increases, diffusion distances increase and the ratio of surface area to volume drops.
  • Diffusion is a slow, passive transport process.
  • Their cells are kept moist so that gases diffuse quickly via direct diffusion.
  • Flatworms are small, literally flat worms, which ‘breathe' through diffusion across the outer membrane .
  • This flatworm's process of respiration works by diffusion across the outer membrane.

• The Diffusion of Innovation

  • The diffusion of innovation theory seeks to explain how, why, and at what rate new ideas and technology spread through cultures.
  • The diffusion of innovation is a theory that seeks to explain how, why, and at what rate new ideas and technology spread through cultures.
  • The origins of the diffusion of innovation theory are varied and span multiple disciplines.
  • Everett Rogers, a professor of rural sociology, popularized the theory in his 1962 book Diffusion of Innovations.
  • He said diffusion is the process by which an innovation is communicated through certain channels over time among the members of a social system.

• Limiting Effects of Diffusion on Size and Development

  • The exchange of nutrients and wastes between a cell and its watery environment occurs through the process of diffusion.
  • Diffusion is effective over a specific distance and limits the size that an individual cell can attain.
  • If the cell is too large, then diffusion is ineffective at completing all of these tasks.
  • The larger the size of the sphere, or animal, the less surface area for diffusion it possesses.
  • This has an effect on diffusion because it relies on the surface area of a cell: as a cell gets bigger, diffusion becomes less efficient.

• The Role of Passive Transport

  • Passive transport, such as diffusion and osmosis, moves materials of small molecular weight across membranes.
  • In solutions containing more than one substance, each type of molecule diffuses according to its own concentration gradient, independent of the diffusion of other substances.
  • Many factors can affect the rate of diffusion, including, but not limited to, concentration gradient, size of the particles that are diffusing, and temperature of the system.
  • In living systems, diffusion of substances in and out of cells is mediated by the plasma membrane.
  • Diffusion is a type of passive transport.

• Transport of Electrolytes across Cell Membranes

  • Ions cannot diffuse passively through membranes; instead, their concentrations are regulated by facilitated diffusion and active transport.
  • Electrolyte ions may not be able to passively diffuse across a membrane, but may instead require special mechanisms to cross the semi-permeable membrane.
  • The mechanisms that transport ions across membranes are facilitated diffusion and active transport.
  • Facilitated diffusion of solutes occurs through protein-based channels.
  • Passive transport, such as diffusion, requires no energy as particles move along their gradient.

• Gas Diffusion and Effusion

  • Diffusion refers to the process of particles moving from an area of high concentration to one of low concentration.
  • Diffusion results in the gradual mixing of materials, and eventually, it forms a homogeneous mixture.
  • Explore the role of a molecule's mass with respect to its diffusion rate.
  • Explore the role of temperature on the rate of diffusion.
  • Compare the diffusion rates at low, medium and high temperatures.

• Osmosis

  • While diffusion transports materials across membranes and within cells, osmosis transports only water across a membrane.
  • The semipermeable membrane limits the diffusion of solutes in the water.
  • Osmosis is a special case of diffusion.
  • However, only the material capable of passing through the membrane will diffuse through it.
  • In this example, the solute cannot diffuse through the membrane, but the water can.