BIO 121 Lecture 4: Bio Lecture 9:17-22:14.pdf
25 Sep 2014
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Net movement of substance down its concentration gradient. 9/22/2014: when lump of sugar is dropped into beaker of pure water, sugar molecules begin to dissolve and diffuse through water. 9/22/2014: sugar molecules continue to dissolve and diffuse through water, eventually sugar molecules become distributed randomly throughout water. What are the components of cell membranes: phospholipids, proteins, polysaccharides, all of the above, none of the above. Detergent molecules are roughly cone-shaped amphipathic molecules that associate in water as spherical structures. Hydrophilic heads at 2 surfaces of bilayer. Phospholipids associate as bilayers in water because they are roughly cylindrical amphipathic molecules. The hydrophobic fatty acid chains are not exposed to water, whereas the hydrophilic phospholipid heads are in contact with water. Interior of cell from external environment: receives information. Passage of materials in and out of cell. To allow separate functions: participates in biochemical reactions. Biological membranes are selectively permeable membranes that help maintain homeostasis in the cell.
