Simple and facilitated diffusion Flashcards
Is diffusion an active or a passive process?
Passive as it does not requires energy
What are the two types of diffusion?
- Simple
- Facilitated
What is simple diffusion?
The diffusion of small and non-polar molecules down a concentration gradient
What are some molecules that can pass through the cell membrane via simple diffusion?
- Oxygen
- Carbon dioxide
Only some molecules can pass through the cell membrane via simple diffusion. Why is this?
- Must be small so that it can pass through the spaces between phospholipids
- Must be non-polar so that they can dissolve in the centre of the membrane
What is facilitated diffusion?
The diffusion of large and polar molecules down a concentration gradient using a protein channel / carrier protein
What two types of proteins are involved in facilitated diffusion?
- Carrier proteins
- Channel proteins
What is the role of carrier proteins?
To transport large / polar molecules across cell membranes
How does a carrier protein transport molecules across a cell membrane?
1) A large molecule attaches to a carrier protein
2) This causes the carrier protein to change shape
3) The carrier protein releases the molecule on the opposite side of the membrane
What is the role of channel proteins?
To transport ions across cell membrane
How does a channel protein transport molecules across a cell membrane?
Forms pores in the cell membrane for ions to diffuse through
What are the factors that affect the rate of diffusion?
- Temperature
- Concentration gradient
- Thickness of membrane
- Surface area
- Number of carrier or channel proteins
How does temperature affect the rate of diffusion?
At higher temps, particles have more kinetic energy and diffuse faster
How does the concentration gradient affect the rate of diffusion?
The higher the concentration gradient, the faster the rate of diffusion
How does the thickness of the membrane affect the rate of diffusion?
Particles travel less distance in thinner exchange surfaces so they will diffuse faster
How does the surface area affect the rate of diffusion?
A larger the surface area mean more particles can cross the membrane at once, so faster diffusion
How does the number of carrier and channel proteins affect the rate of diffusion in facilitated diffusion?
The more carrier and channel proteins there are, the faster the rate of diffusion
In facilitated diffusion, the rate of diffusion will increase as concentration increases however will eventually plateau while concentration is still increasing. Why is this?
All of the carrier and channel proteins are saturated and cannot work any faster
- They are limiting factors
