BIO 101 Lab 4, Osmosis and Dialysis-1.docx - BIO 101 Lab 4...

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BIO 101 Lab 4: Osmosis and Dialysis To submit, print or edit ( in a different color ) this lab, complete the activities, scan your work using the free AdobeScan app on your phone or save your document, and upload your scanned PDF or Word file to Canvas. If you have a disability that makes it difficult to complete this lab, please contact your instructor. Please provide your instructor a copy of the Memorandum of Accommodation (MOA) from NVCC Disability Support Services. Objectives: Review cell membrane structure and the components that make it a semipermeable barrier. Observe the effect of virtual cells placed in solutions, hypotonic, isotonic, and hypertonic to the cells Background: Cells and Cell Membrane structure Living cells are filled with an aqueous solution, the cytosol. Many small solutes or particles, are dissolved in this watery cytosol, including ions, nutrients, waste and enzymes. Larger organelles (such as mitochondria and chloroplasts) and large complexes of molecules (e.g. ribosomes) are also located in this cytosol; organelles and complexes combine with the cytosol to form the cytoplasm of cells. The exterior barrier of all cells, is a cell membrane (plasma membrane). Because the cell membrane is comprised of both phospholipids and proteins it is semi-permeable: select molecules can easily pass through the phospholipid bilayer, while other molecules cannot. Phospholipids are comprised of hydrophobic fatty acid tails and polar phospho- heads. In the bilayer, the fatty layers are sandwiched in between the hydrophilic polar heads; one layer of polar heads lines the inside (cytosolic face) of the cell membrane and a second polar head, lines the outside of the cell membrane or surface. Transport through membranes Molecules that can easily pass through a cell membrane are small and nonpolar, such as gases: oxygen, carbon dioxide, and nitrogen. Hydrophobic lipids, (fats and steroids) can dissolve in the hydrophobic fatty layer of the cell membrane and also will diffuse into or out of a cell.

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