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Flashcards in transport mechanisms through a membrane Deck (15):


• Is the net movement of particles from a region of high concentration to a region of lower concentration until they are equally distributed.
• It is a passive process (i.e. it doesn’t require energy. Particles move die to their natural kinetic energy)


where does diffusion happen?

• In living and non-living system wherever there is a concentration gradient and no barrier to the movement
• When substances can freely move through the membranes


what factor effects the rate of diffusion?

• The greater the difference between the concentrations the faster the rate of diffusion
• Smaller particles diffuse faster than larger ones
• The shorter the distance the faster the rate of diffusion
• Increase in temperature increases the kinetic energy of particles, therefore rate of diffusion increases


facilitated diffusion

• Net movement of particles from an area of higher concentration to an area of lower concentration
• Uses carrier proteins and channel proteins to aid the diffusion of large molecules and charged particles through the membrane.
• Passive process- doesn’t require energy



if the channel/carrier proteins are specific to one type of substance.



Symports- if 2 or more different molecules/ions in the same direction



• Osmosis is the net movement of water molecules from a region of higher water potential to a region of lower water potential, through a semi permeable membrane/ partially permeable membrane.
• Passive process- doesn’t require energy


water potential definition

• Is the potential (likelihood) of water molecules to diffuse out off or into a solution.
• ‘The measure of the ability of water molecules to move freely in solution'


water potential

• Smaller molecules can diffuse easily through the cell membrane, whereas bigger molecules can’t.
• Pure water has a water potential of zero. Adding solutes to pure water lowers its water potential- so the water potential of any solution is negative. The more negative the water potential the stronger the concentration of the solutes in the solution


water potential equation

• Water potential= solute potential + pressure potential



• Hypertonic- lower ψ (more solute) – shrinks



• Isotonic – same ψ (equal solute)



• Hypotonic – higher ψ (less solute)- swells up


describe how you could use your results to find water potential

1. draw graph
2. find where the line intersects the x axis
3. research on the internet to find the conversion concentration


how can you investigate the water potential of a plant cell? required practical 3

1. make up dilutions of solution
2. cut potato into equal size pieces
3. blot the potato with a paper towel and weigh them
4. put the potatoes into the different solutions
5. take the potato chips out and blot them
6. weigh them
7. work out the change in mass
8. work out the percentage mass change
9. draw a graph