The Cell Membrane And The Membrane Essay

1531 Words Sep 11th, 2016 7 Pages
The cell has several different ways that it allows molecules and ions to cross its membrane, including bulk transport, osmosis, passive transport, and active transport. The purpose of the cell membrane is to protect the cell and only allow specific substances to cross the membrane, such as amino acids or water. Lipids hold the membrane together, along with proteins and carbohydrates. These lipids are saturated or unsaturated, and have a hydrophilic head. The tails hold the membrane together due to their fear of water. Carbohydrates are marbled throughout the cell membrane, reducing the fluidity of the membrane and making it more difficult for nonpolar substances to cross. Transport channels and proteins are also part of the membrane, that assist in facilitated diffusion. Bulk transport includes pinocytosis, phagocytosis, endocytosis, exocytosis, and receptor mediated endocytosis. During pinocytosis, the cell takes small amounts of extracellular fluid and pulls them into vesicles through the cell membrane almost constantly. Phagocytosis is where the cell engulfs food or other molecules by extending pseudopodium and enclosing the molecules before pulling them into the cell. From there, the pseudopodium becomes a food vacuole and is digested after fusing with a lysosome. Endocytosis is where part of the cell membrane fuses with a vacuole to pull extracellular fluid and other molecules into the membrane. Exocytosis is almost the same as endocytosis, however the cell is…

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