Consider the plasma membrane and the key features of the Fluid Mosaic Model: A) What is the fundamental structural aspect of the membrane (p. 159-168)? B) What components are needed for materials to pass in and out of the cell? (p. 169-180)
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1. The modern understanding of the cellular or plasma membrane is referred to as the fluid mosaic model or lipid bilayer model. 2. It is composed of a bilayer of phospholipids. 3. Glycoproteins are attached to some of the proteins and lipids on the outward-facing surface of the membrane. 4. Cell recognition is a function of carbohydrates. 5. The fluid nature of the membrane is due to phospholipids. 6. Cell membranes separate and protect the borders of cells. 7. Membrane transport refers to the collection of mechanisms that regulate the passage of solutes. 8. Integral proteins are integrated into the membrane structure that interacts extensively with the hydrocarbon chains of membrane lipids.
Lainey R.
After thoroughly reviewing the material, put together a study aid with key information for each term. Always describe the relevant structure/molecule for each item, its function, and its biological significance/meaning/connections with other players in the same process. Keep in mind that the amount of information can vary significantly between subtopics. 4. Lipid bilayer permeability: What properties of the molecules are critical for crossing the cellular membrane? What types of molecules easily cross the membrane? What types of molecules cannot cross the membrane by themselves and why? 5. Channels vs. pores: Definition. Mechanism of forming a hydrophilic passage through the hydrophobic lipid bilayer. 6. Types of nonvesicular membrane transport: active vs. passive (including how each one can be achieved on the molecular level); transport of single vs. multiple molecules. 7. Types of vesicular transport: endocytosis vs. exocytosis vs. transcytosis; pinocytosis vs. phagocytosis vs. receptor-mediated cytosis. 8. Cholesterol transport and health significance: What does the cell use cholesterol for.
Madhur L.
Cells are bounded by membranes composed of phospholipids. A phospholipid consists of a pair of fatty acids that may or may not have carbon-carbon double bonds, fused at the carboxylic acid with a three-carbon glycerol that is terminated by a phosphate, as shown in the figure below. Most cell membranes comprise two phospholipid layers with the hydrophilic phosphate ends of each molecule in the outer and inner surfaces. The hydrophobic chains of carbon atoms extend into the space between these two surfaces. The exchange of matter between the interior of the cell and the environment is mediated by this membrane with selective permeability. A. Pose questions that identify the important characteristics of this lipid bilayer structure the molecules that must be acquired from the environment and eliminated from the cell relationships between the structures of these molecules and the structure of the bilayer Because the plasma cell membrane has both hydrophilic and hydrophobic properties, few types of molecules possess structures that allow them to pass between the interior of the cell and the environment through passive diffusion. The fluidity of the membrane affects passive transport, and the incorporation of other molecules in the membrane, in particular cholesterols, has a strong effect on its fluidity. Fluidity is also affected by temperature. Measurements of the speed of movement of oxygen molecules, $\mathrm{O}_{2},$ through three types of membranes were made (Widomska et al, Biochimica et Biophysica Acta, $1,768,2007$ and compared with the speed of movement of $\mathrm{O}_{2}$ through water. These measurements were carried out at four different temperatures. One type of membrane was obtained from the cells in the eyeball of a calf (lens lipid). Synthetic membranes composed of palmitic acid with cholesterol (POPC/CHOL) and without cholesterol $($ POPC) were also used. The results from these experiments are shown in the table below. B. Represent these data graphically. The axes should be labeled, and different symbols should be used to plot data for each material. C. Analyze the data by comparing transport of oxygen through the biological membrane, water, and the synthetic membranes. Consider both membrane composition and temperature in your analysis. The plasma membrane separates the interior and the exterior of the cell. A potential to do work is established by defining regions inside and outside the cell with different concentrations of key molecules and net charge. In addition to the membrane defining the cell boundary, eukaryotic cells have internal membranes. D. Explain how internal membranes significantly increase the functional capacity of the cells of eukaryotes relative to those of prokaryotes.
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