Biology AQA 3.1.3 Osmosis and Diffusion

Question	Answer
Osmosis	The passive movement of molecules from a region of high water potential to low, along the concentration gradient. this is done across a partially permeable membrane
Isotonic	A solution which stops osmosis so that osmotic lysis doesn't occur and bursts the cells
Diffusion	The passive movement of molecules along the concentration gradient
How does Surface Area affect diffusion?	The larger the surface area to volume ratio, the greater the rate of diffusion because of more pathways
How does Concentration affect Diffusion?	more concentration in one area and less in another would be a quick rate, however if the concentration is similar in both areas it will remain around the same
How does the thickness of exchange surfaces affect diffusion?	The thinner the membrane, the quicker the rate of diffusion
Facilitated diffusion	Allows molecules to pass across a plasma membrane. Protein channels: regulated by the cell to allow molecules across. They can close and open. Carrier proteins: Bind to specific molecules, ATP is needed to open the channel on the opposite side, it attachs and forms ADP P, once the molecules crosses it unbinds causes channel to return back to its normal shape

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	Created by evie.daines over 10 years ago