5.3 Diffusion Flashcards
What is diffusion
Net or overall movement of particles from a region of higher concentration to lower concentration
Passive process until equilibrium is reached
Why does rate of diffusion decreases the longer the conc gradient gets
More cells will collide and slow down the passive movement
What are the factors affecting the rate of diffusion
Temperature
Concentration difference
What is simple diffusion
Diffusion in teh absence of a barrier or membrane
What substances are repelled by the hydrophobic interior of membranes
And what substances can diffuse straight though
Substances with a positive or negative charge - ions
Polar molecules with partial positive and partial negative at a very slow rate
What affects the rate at which molecules diffuse across membranes
Surface area - larger the area of exchange the higher the rate
Thickness of membrane
How do polar molcules and ions pass through membranes
And what is this process called
Through channel proteins
Facilitated diffusion
What are membranes called with protein channels
Selectively permeable
Does facilitied diffusion need energy
No as it’s down a conc gradient
