5.3 Diffusion Flashcards
Define passive transport
Passive - doesn’t require energy from respiration
Define diffusion.
Movement of particles from high concentration to low concentration down a concentration gradient.
Why is diffusion fast at short distances?
Why is rate of diffusion slower over long distances?
Particles move at high speed and are constantly colliding. This slows down their overall movement.
More collisions have occurred.
What factors affect rate of diffusion?
- Temperature
- Concentration difference
- Surface Area
- Thickness of membrane
How does temperature affect diffusion rate?
Higher diffusion rate - particles have more kinetic energy so move faster
How does concentration difference affect diffusion rate?
The greater difference in concentration the faster diffusion - bc from high conc. to low conc, overall movement is larger
How does surface area affect diffusion rate?
Larger area of exchange surface = faster diffusion
How does membrane thickness affect diffusion rate?
Thinner exchange surface = faster diffusion
Why are membranes said to be partially permeable?
Hydrophobic core repels positive + negative charge.
Polar molecules are slightly positive + negative, so can pass through
What is facilitated diffusion?
Diffusion across membrane through protein channels down a concentration gradient
Protein channels are specific to one one molecule. What is this called in terms of permeability?
Selectively permeable
What 5 factors affect rate of facilitated diffusion?
- Temperature
- Concentration difference
- Surface area
- Membrane thickness
- Amount of channel proteins
