movement of substances in and out of cells Flashcards
what is diffusion
the net movement of particles from an area of high concentration to an area of lower concentration
is diffusion on a passive or active process
passive - it does not require energy
state –> diffusion happens in both liquids and gases bcs the particles in these substances are free to move about randomly
state –> the bigger the difference in concentration, the faster the diffusion rate
in the cell membrane…
substances can move in and out of the cell by diffusion, osmosis, and active transport
what molecules can diffuse through cell membranes
small molecules like amino acids, glucose, water, and oxygen can diffuse through the membrane but big molecules like starch and proteins cannot
state –> particles flow through the cell membrane from where theres a higher concentration to where theres a lower concentration
what is osmosis
the net movement of water molecules across a partially permeable membrane from a region of higher concentration to a region of lower water concentration
whats a partially permeable membrane
is just one with very small holes in them, so tiny molecules like water can pass through but bigger molecules like sucrose cant
how to investigate osmosis - practical
Prepare Potato Samples:
Cut equal-sized potato cylinders using a knife or cutter.
Measure and record their initial length and mass.
Prepare Solutions:
Label beakers with different sugar concentrations.
Add solutions to the beakers.
Submerge Potatoes:
Place one potato cylinder in each beaker.
Ensure the potato is fully submerged.
Wait for Osmosis:
Leave the potatoes in the solutions for a fixed time (e.g., 30 minutes to 1 hour).
Measure Final Mass and Length:
Remove the potato cylinders, blot them dry with a paper towel.
Measure and record their final length and mass.
if cylinders have drawn in water by osmosis, they’ll be be a bit longer, if water has been drawn out then they’ll have shrunk a bit.
visking tubing - non living systems
- fix some visking tubing over the end of a thistle funnel then pour some sugar solution 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.
what is active transport
its the movement of particles against a concentration gradient (ie from an area of low concentration to an area of high concentration) using energy released during respiration
4 factors that affect the movement of substances
- surface area to volume ratio
- distance
- temperature
- concentration gradient
surface area to volume ratio
-the rate of diffusion, osmosis and active transport is higher in cells (or cubes) with a larger surface area to volume ratio
distance
if substances only have a short distance to move, then they will move in and out of the cell faster. for example, cell membranes are very thin
temperature
as the particles in a substance get warmer they have more energy- so they will move faster. this means as temperature increases, substances move in and out of the cells faster
concentration gradient
substances move in and out of a cell faster if there is a big difference in concentration between the inside and the outside of a cell.
- if there are lots mor particles on one side, there are more there to move across
- this only increases the rate of diffusion and osmosis though- concentration gradient dont affect the rate of active transport
state- with active transport increasing the concentration does not have an affect on the results
