exam 2 1510 - Transmembrane domains are composed of...

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Transmembrane domains are composed of hydrophobic amino acids that are usually arranged into alpha helices. Example of a protein with a single Transmembrane domain is the linking protein that attaches the spectrin network of the cytoskeleton to the interior of the plasma membrane. Another example is bacteriorhodopsin, one of the key Transmembrane proteins that carries out photosynthesis in halophilic archaea. Passive transport is when substances move in and out of the cell without the cell’s having to expend energy. Transport can occur by simple diffusion, which is movement of substances going from high concentration to lower concentration. Proteins allow membrane diffusion to be selective Channel proteins have a hydrophilic interior that provides and aqueous channel through which polar molecules can pass whine the channel is open Carrier proteins in contrast to channels bind specifically to the molecule they assist much like an enzyme binds to its substrate. These channels and carriers are usually selective for one type of molecule and thus the cell membrane is said to be selectively permeable. Ions cant move between the cytoplasm of a cell and the extracellular fluid without
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exam 2 1510 - Transmembrane domains are composed of...

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