Factors Affecting Diffusion
i) Concentration: the difference in the amount of a substance on either side of the membrane (the steepness of the gradient). The greater the difference, the higher the rate of diffusion. ii) Temperature : the higher the temperature, the faster the rate of diffusion. iii) Mass : the larger the mass of the diffusing particle, the slower the rate of diffusion. iv) Surface Area : larger the surface area available for diffusion, faster the rate of diffusion. v) Distance : the thickness of the membrane that a substance must dissolve across. The greater the distance, the slower the rate of diffusion.
Factors Affecting facilitated diffusion:
i) Transport Maximum : the maximum number of transport proteins available ii) Saturability: the ability of the plasma membrane to have all transport proteins in use.
2) Osmosis : Water moving across a selectively permeable membrane (higher water concentration to lower water concentration). Water moves across the lipid bilayer by simple diffusion or by aquaporins which are integral membrane proteins functioning as water pores. Osmosis only occurs when a membrane is permeable to water.
Tonicity: the ability of a solution to change cell volume by altering its water content via Osmosis. (Related to SOLUTE concentration!!)
Isotonic solution: Same number of solutes on either side
Hypotonic solution: lesser concentration of solutes & more water in the solution
Hypertonic solution: greater concertation of solutes & less water in the solution
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