zarahh09
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Diffusion occurs through the phospholipid bilayer. Explain what type of substance will be able to move into/out of cells this way.
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ItsMeAbdul
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Small uncharged polar molecules, such as H2O, also can diffuse through membranes, but larger uncharged polar molecules, such as glucose, cannot. Charged molecules, such as ions, are unable to diffuse through a phospholipid bilayer regardless of size; even H+ ions cannot cross a lipid bilayer by free diffusion.

Hope that helps
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Hellllpppp
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(Original post by ItsMeAbdul)
Small uncharged polar molecules, such as H2O, also can diffuse through membranes, but larger uncharged polar molecules, such as glucose, cannot. Charged molecules, such as ions, are unable to diffuse through a phospholipid bilayer regardless of size; even H+ ions cannot cross a lipid bilayer by free diffusion.

Hope that helps
I thought it was small and/or non-polar molecules. Isn’t ‘uncharged polar’ a contradiction.
Last edited by Hellllpppp; 1 month ago
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ItsMeAbdul
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(Original post by Hellllpppp)
I thought it was small and/or non-polar molecules. Isn’t ‘uncharged polar’ a contradiction.
Uncharged polar basically means non-polar
U are on the right path
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Bookworm_88
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(Original post by ItsMeAbdul)
Small uncharged polar molecules, such as H2O, also can diffuse through membranes, but larger uncharged polar molecules, such as glucose, cannot. Charged molecules, such as ions, are unable to diffuse through a phospholipid bilayer regardless of size; even H+ ions cannot cross a lipid bilayer by free diffusion.

Hope that helps
I would like to add that simple (aka free) diffusion occurs for lipid soluble, small uncharged molecules e.g CO2 and 02.
Facilitated diffusion involved carrier proteins where specific substances bind to specific carrier proteins which change shape in a way that transports substance across the mem. this is for large, polar molecules and ions.

(Original post by Hellllpppp)
I thought it was small and non-polar molecules. Isn’t ‘uncharged polar’ a contradiction.
Yeah.
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Hellllpppp
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(Original post by ItsMeAbdul)
Uncharged polar basically means non-polar
U are on the right path
I think for A-level (at least for AQA) you need to say non-polar not uncharged polar. I’ve done a quick google search and I now understand what you mean by uncharged polar
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