movement of substances Flashcards
diffusion
-the movement of particles from areas of higher concentration to areas of lower concentration
-passive process-no energy
-happens in liquids and gases - particles in these substances are free to move about randomly
what molecules can fit into cell membranes
glucose, amino acids, water and oxygen can diffuse through cell membranes
osmosis
the net movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration
-passive process - no energy
what is a partially permeable membrane
a membrane with very small holes in it, only tiny molecules like water can pass through them
-cell membranes are partially permeable membranes
investigate diffusion in non living system
-make up some agar jelly with phenolphthalein and dilute sodium hydroxide(pink)
-put some dilute hydrochloric acid in a beaker
-cut out a few cubes from the jelly and put them in a beaker
-if you leave the cubes for a while they will turn colourless as the acid diffuses into the agar jelly and neutralises the sodium hydroxide
investigate osmosis in living system
-cut up a potato into identical cylinders and get some beakers with different sugar solutions in them
-one is pure water, another is very concentrated sugar solution, and a few concentration in between
-measure the length of the cylinders, then leave a few cylinders in each beaker for half an hour
-take them out ad measure their lengths again
- if the cylinders have drawn in water by osmosis, they will be a bit longer, if water has been drawn out, they will shrink,
-plot a graph to see the concentration of potato
investigate osmosis in non living system
-fix some visking tubing over the end of a thistle funnel
-pour some sugar solution down the glass tube into the thistle funnel
-put the thistle funnel into a beaker of pure water- measure where the sugar solution comes up to on the glass tube
-leave the apparatus overnight, then measure where the solution is in the glass tube
-water should be drawn through the visking tubing by osmosis and this will force the solution up the glass tube
active transport
-the movement of particles against a concentration gradient using energy released during respiration
factors affecting movement of substances
-surface area to volume ratio
-distance
-temperature
-concentration gradient
how does surface area to volume ratio affect the movement of substances
-the rate of diffusion, osmosis and active transport is higher in cells with a larger surface area to volume ratio
how does distance affect the movement of substances
-substances travelling a short distance will move in and out of cells faster
how does temperature affect the rate of movement of substances
-as the particles in a substance get warmer they have more energy, so they move faster
-this means as temperature increases, substances move in and out of cells faster
how does concentration gradient affect the rate of movement of substances
-substances move in and out of a cell faster if there is a big difference in concentration between the inside and outside of the cell
-lots more particles on one side, there are more particles to move across,
-only increases the rate of diffusion and osmosis, not active transport
