Diffusion Flashcards
UNIT #1
What is diffusion?
Diffusion is the NET movement of particles of a GAS or a SOLUTE from an area of HIGH concentration to an area of LOW concentration.
Why is it called the net movement of particles?
Because more particles move from an area of HIGH concentration to an area of LOW concentration than from low concentration to high concentration.
How temperature affects the rate of diffusion?
TEMPERATURE; if this increases, then the particles have more KINETIC energy and move faster
How the diffusion gradient affects the rate of diffusion?
The diffusion GRADIENT; the greater the difference in comcentrations between the two regions, the GREATER the net movement of particles
How the diffusion path affects the rate of diffusion?
The DIFFUSION PATH; i.e. how far the particle has to move
How the surface area affects the rate of diffusion?
The SURFACE AREA; the greater this is, the more particles can movie at any one time.
Why is diffusion efficient in unicellular organisms?
Unicelluar organisms are small enough that diffusion across the cell membrane is sufficient to supply the cell with all it needs to survive. This is because they have a large SURFACE AREA.
Why is diffusion not efficient in multicellular organisms?
Multicellular organisms have to have specialised EXCHANGE and transport systems to ensure that substances reach all cells. This is necessary because as the size of an organism increases, the surface area: volume decreases so DIFFUSION alone is insufficient to supply all cells with oxygen and food.
What happens in the lungs?
In the lungs, OXYGEN diffuses into the red blood cells from the air down a concentration gradient and CARBON DIOXIDE diffuses from the blood into the air. Urea diffuses out of cells into blood plasma and is excreted by the KIDNEYS.
How can cells be adapted?
Cells can be adapted to increase the rate of diffusion by having a cell membrane that is folded to form MICROVILLI. This greatly increases their SURFACE AREA. An example of this epithelial cells that line the SMALL INTESTINE and absorb the products of digestion. The lining of the small intestine is also folded into 1mm projections called VILLI.
What makes this process take place?
The random movement of particles.
