Exchange Across Cell Membranes - Diffusion Flashcards
What is diffusion
The net movement of particles from an area of higher concentration to an area of lower concentration
What ways will molecules diffuse
Molecules will diffuse both ways
When will diffusion stop occuring
When all particles are evenly distributed around the liquid or gas
What is the concentration gradient
The path from an area of higher concentration to an area of lower concentration.particles diffuse down a concentration gradient
What type of process is diffusion
A passive process,in which no energy is needed
Why can oxygen and carbon dioxide diffuse easily through the cell membranes
Due to them being so small meaning they can pass through the phospholipids
Oxygen and carbon dioxide are non-polar what does this mean
This makes them soluble in lipids,so they can dissolve in the hydrophobic layer
What is it known as when molecules diffuse directly through a cell membrane
Simple diffusion
What are some examples of larger molecules that diffuse slowly
Amino acids,glucose
Why would charged particles diffuse slowly
They are water soluble and the centre of the bilayer is hydrophobic
What are examples of charges particles
Ions and polar molecules
What is facilitated diffusion
A process to speed up diffusion in which large or charged particles diffuse through carrier protein or channel proteins
What type of process is facilitated diffusion
A passive process not requiring energy
What are the three steps of carrier proteins
1) a large molecule attaches to o a carrier protein in the membrane
2) then,the protein changes shape
3) this releases the molecule on the opposite side of the membrane
How does the concentration gradient affect rate of diffusion
Teh higher it is,the faster the rate of diffusion.As diffusion takes place,the difference in concentration between thee two sides of the membrane decreases until it reaches an equilibrium
How does the thickness of the exchange surface affect rate of diffusion
Teh thinner the exchange surface (i.e. the shorter the distance the particles have to travel) the faster the rate of diffusion.
How does the surface area affect rate of diffusion
The larger the surface area (e.g. of the cell-surface membrane) the faster the rate of diffusion
What does facilitated diffusion depend on
The concentration gradient
The no. Of channel or carrier proteins
How does the concentration gradient affect facilitated diffusion
The higher the concentration gradient,the faster the rate of facilitated diffusion. As equilibrium is reached,the rate of diffusion will level off.
Why does facilitated diffusion depend on the no. Of channel or carrier proteins
Once all the proteins in a membrane are in use, facilitated diffusion can’t happen any faster.so the greater the number of channel or carrier proteins the faster the rate.
