Diffusion Flashcards
What is diffusion?
The net movement of molecules/ions down the concentration gradient from an area of high concentration to an area of less concentration until they are evenly distributed.
What is simple diffusion?
a passive method of transport across the cell membrane via the phospholipid bilayer, involving non polar molecules.
What are polar molecules soluble in?
Non polar?
Polar are water soluble.
Non-polar are fat soluble.
How does concentration gradient affect rate?
The bigger the difference, the faster the rate.
How does surface thickness affect the rate of diffusion?
If it is a thinner surface, the distance to be travelled is less so the rate is faster.
Surface area?
the larger the surface area, the greater the chance of colliding with a boundary so the rate is faster.
What molecules can diffuse across the plasma membrane?
what is this known as?
small non-polar molecules such as oxygen or carbon dioxide.
this is simple diffusion.
What is facilitated diffusion?
a passive method of transport accross membranes involving carrier proteins and channel proteins.
Which molecules are involved in facilitated diffusion?
Charged ions or polar molecules which have to be aided by protein channels or carrier proteins.
What are protein channels?
water filled hydrophilic channels which allow water soluble ions to pass through.
what are protein channels to particular ions?
they are specific or complementary to them.
Why does the protein channel close if the ion it is specific to isn’t present?
to control the entry and exit of ions.
What happens when the ion binds with the protein?
the protein changes shape and the membrane closes on one side and opens on the other.
what are carrier proteins?
they are specific/complementary to molecules.
what do carrier proteins do when a molecule such as glucose is present?
it binds to the protein, which causes a change of shape to the protein so the glucose is released on the other side.
