BI236 Lecture Notes - Lecture 9: Lipid Bilayer, Golgi Apparatus, Osmosis
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Document Summary
Asymmetrical distribution of proteins, lipids, and associated carbohydrates in the plasma membranes is determined when the membrane is built (by the er and. Golgi apparatus): movement of materials across cell membranes. Hydrophobic (non-polar) molecules, such as hydrocarbons, can dissolve in the lipid bilayer and pass through the membrane rapidly. Polar molecules do not cross the membrane easily. From a thermodynamic point of view there are only 3 types of transport processes: passivetransport: Passive transport is movement of molecules through the membrane in which; Molecules move in response to a concentration gradient. Passive transport is diffusion of a substance across a membrane with no energy investment. Diffusion is movement of molecules from high to low concentration. It"s the tendency for molecules to spread out evenly into the available space. Substances diffuse down their concentration gradient, which requires no work. Diffusion across a biological membrane is passive transport. Osmosis is the diffusion of water across a selectively permeable membrane.