3.1 diffusion Flashcards
define diffusion
the net movement of ions and molecules from a region of higher concentration to a region of lower concentration down a concentration gradient, as a result of their random movement
what causes a faster movement of ions and molecules?
higher temperature
give examples of diffusion in living things
oxygen moves down a concentration gradient from the air in the alveoli to the blood; carbon dioxide moves down a concentration gradient from the blood to the air in the alveoli
why does diffusion not occur through the human skin, unlike earthworms?
there are too many layers of cells for diffusion to be fast enough
why can’t all substances diffuse in a cell?
if all kinds of substance could diffuse into a cell, there would be a danger that poisonous substances could diffuse in and kill the cell
why can’t all substances diffuse out of a cell?
if all the substances in a cell could diffuse out, the cell would lose essential substances (e.g. glucose) needed to keep the cell alive
how fast is diffusion?
diffusion is rapid enough to keep a cell supplied with oxygen and food; for living processes it is effective only over short distances
how do carbon dioxide and oxygen diffuse in a leaf?
carbon dioxide and oxygen diffuse through the pores in the epidermis and into the spaces between the cells
what is the distance between the membrane of the cell to the centre of the cell?
<0.1mm
what is the approximate diameter of an air sac in the human lung?
0.06mm
why does diffusion occur faster in hot temperatures?
the higher the temperature, the more kinetic energy the particles will have, so they will move and mix more quickly
what are the factors that affect the rate of diffusion?
- temperature
- surface area of cell membrane separating different regions
- concentration gradient
