Diffusion Flashcards
1
Q
Diffusion
A
- Diffusion is the net movement of molecules from an area of high concentration to an area of low concentration until equilibrium is established
- It is a passive process
- Small particles like oxygen and carbon dioxide are able to enter and leave the cell via diffusion
- Non- polar lipids (fats) are also able to diffuse directly through the cell membrane.
- The higher the concentration gradient, the greater the rate of diffusion
2
Q
Facilitated diffusion
A
- Some materials are unable to diffuse through the cell membrane due to size or polarity so must enter via facilitated diffusion.
- Definition: In facilitated diffusion (aka passive carrier mediated transport) materials move from an area of high concentration to and area of low concentration, using channel or carrier proteins. It is a passive process.
- How it works: In facilitated diffusion the substance binds to a specific carrier protein causing it to change shape, and allow the substance to cross the cell membrane.- this does not require any energy
- Examples: Amino acids and glucose are transported via facilitated diffusion.
- Rate of facilitated transport: As concentration goes up, the rate will also go up, but only up to a certain point. The rate will stop going up when all channel proteins are in use.
3
Q
What are factors that affect rate of diffusion?
A
- Concentration gradient: The greater the difference in concentration, the greater the rate of diffusion and vice versa.
- Temperature: the higher the temperature, the more energy the particles have and thus move faster and collide with the membrane more, increasing rate of diffusion and vice versa.
- Particle size: It is more difficult for larger particles to diffuse across the membrane
- The larger the particle the lower the rate of diffusion and vice versa.
- Surface area: The greater the available surface area, the more available space for particles to diffuse
- Higher surface area results in a higher rate of diffusion and vice versa
- Diffusion distance: The greater the diffusion distance, the more time it takes for particles to diffuse thus lowering the rate of diffusion
