tutorial 7 study guide.docx - The Cell Membrane u25cf Cell...

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The Cell Membrane Cell membranes physically define and separate the cell from its environment Four general roles membranes play in the cell: 1. Defines the boundary of the cell and acts as a semi-permeable barrier that restricts movement of substances in or out of the cell 2. Membranes surround and define organelles such as the mitochondria or nucleus so that contents of organelles cannot mix freely with cytoplasm 3. Regulate transport of molecules in and out of the cell, and between organelles and the cytoplasm 4. Receives signals from the environment, often in the form of small molecules or proteins that are detected by specific receptors and change the cell Components of the biological membrane contain lipids and proteins Bilayer with proteins embedded or associated as well as carbohydrates Carbs are less abundant and linked to either lipids or proteins Amphipathic nature of phospholipids allows formation in water Proteins are also amphipathic with hydrophobic region toward the tails and hydrophilic region toward the heads Selective permeability: Some molecules can readily pass through, others cannot. They must use transport proteins Nonpolar molecules can dissolve in the lipid bilayer passively (without energy) Polar molecules are impeded by hydrophobic core and need transport proteins Water uses aquaporins as a form of active transport (with energy)
Protein Production and the Organelles Involved Differences between eukaryotic and prokaryotic cells Despite some prokaryotes having organelles, they contain much less sub- cellular architecture The Nucleus: provides genetic information to the cell, surrounded by a double

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