Cell Transport
Transport Across Lipid Bilayer
The selective permeability of biological membranes to small molecules allows the cell to control and maintain its internal composition. Only small uncharged molecules can diffuse freely through phospholipid bilayers (Figure 2.49). Small nonpolar molecules, such as O2 and CO2, are soluble in the lipid bilayer and therefore can readily cross cell membranes. 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. Image: Permeability of phospholipid bilayers. Small uncharged molecules can diffuse freely through a phospholipid bilayer. However, the bilayer is impermeable to larger polar molecules (such as glucose and amino acids) and to ions. Phospholipid Bilayer Self Assembly
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From: Cell Membranes
The Cell: A Molecular Approach. 2nd edition. Cooper GM. Sunderland (MA): Sinauer Associates; 2000. Copyright © 2000, Geoffrey M Cooper. NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health. More on Diffusion HereMore one Osmosis HereMore on Facilitated Diffusion HereMore on Active Transport Here |
Cell membrane in the Neuron
Modeling the Neuron Cell System
Choice #1:
Create a digital version of the neuron system using the Stella Modeling Software. |
Choice #2:
Investigate the effects of consuming different types of fats in your diet on the function of the cell membrane.
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