Diffusion

Diffusion Is a passive (no energy is required) process of moving molecules / substances from one area to another! It involves moving the substances down a concentration gradient from a high to a low solution!

Diffusion High concentration is an area where there is a lot of the substance / molecules in question. The low concentration is the opposite. . An area where there are only a few molecules of the substance!

MINDMAP

Diffusion - Introduction The exchange of substances between cells and the environment occurs in ways that require metabolic energy (______________ ) and in ways that do not (_____________ ). Diffusion is an example of _____________ . ACTIVE TRANSPORT PASSIVE TRANSPORT PASSIVE TRANSPORT

Diffusion is…….. The passive, net movement of particles from an area of high concentration to an area of low concentration, until equilibrium is reached. Due to the random movement of particles. The more kinetic energy the particles have, the faster diffusion occurs.

Diagrammatic version……..

Facilitated Diffusion Exactly the same principles as simple diffusion: Down a concentration gradient Passive Uses Carrier Proteins or Channel Proteins.

Carrier Proteins Carry large water soluble substances e.g. glucose Specific molecules binds with the proteins Causes it to change shape Molecule is released on the other side of the membrane (the carrier protein then converts back to its original shape) No external energy is required Kinetic energy of the molecules themselves is all that’s needed

Carrier Proteins Bind to the substances and undergoes structural changes that allow them to carry the molecules through the membrane

Facilitated Diffusion

Channel Proteins water filled pores, carry ions e.g. Na+ and Ca2+ Water filled channels Molecules such as glucose, amino acids can pass through Selective, only specific molecules are let through If the molecule is not present they remain closed. Control entry and exit of substances

Extracellular space Cytooplasm (aqueous) High concentration Fat-soluble organic molecules can diffuse through the bilayer but polar molecules require proteins Fat-soluble molecules Polar molecules Extracellular space Ion channel Cytooplasm (aqueous) Low concentration hydrophilic pore

Passive (no energy required) Give 2 ways in which facilitated diffusion and simple diffusion are similar and one way in which they are different. Similarities Passive (no energy required) Particles move down their concentration gradient Differences Facilitated diffusion uses proteins

Rate of diffusion! Diffusion is faster in gasses than in solutions! Liquid molecules have lower levels of energy to move and also have to change direction more as the particles are much closer together!

Concentration gradient! The steeper the gradient the faster the rate of diffusion! High concentration Low concentration

The concentration gradient decreases with distance High concentration of Carbon dioxide Low concentration of Carbon dioxide A B Diffusion rate decreases the further away from the cell membrane the organelles are!

Size of the particles Smaller particles like oxygen move faster than carbon dioxide. So the rate of diffusion also depends on the size!

Active Transport https://www.youtube.com/watch?v=bNU5dLp72Ok

Active Transport Inside of cell Outside of cell ATP ADP P