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The cell is the smallest unit of life. All organisms are composed one or more cells. New cells arise from previously existing cells.
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Basic Cell Structure Each cell has four common components: 1.Plasma membrane 2.Region containing DNA 3.Cytoplasm 4.Biochemical molecules & biochemical pathways
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Fluid mosaic model: Working model of the membrane Protein molecules bobbing in phospholipid sea Proteins determine membrane’s specific functions
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Phospholipids Most abundant lipid Polar/hydrophilic head(attracted to water) Pair of nonpolar/hydrophobic tails(repelled by water)
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Hydrophilic head Hydrophobic tails
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Polar heads, outside & inside Nonpolar tails in the interior cell membranes
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Microvilli- intestinal cells Membrane Junctions Tight junctions (impermeable) - stomach Desmosomes (anchor) - skin & heart muscle Gap junctions(communication/electrical activity) - heart & smooth muscle
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Selectively permeable- allows certain substances to pass through By 2 ways: active or passive transport Passive- downhill Active- uphill (needs energy)
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Passive: downhill reaction Simple diffusion Osmosis Facilitated diffusion Filtration Active: uphill reaction, needs ATP Exocytosis Endocytosis - Pinocytosis - Phagosytosis
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No Barrier: Substances “spread out” High concentration to low concentration e.g.: Red dye placed in glass of water
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Substances diffuse High concentration to low concentration Pores in membrane must be large “Down the concentration gradient” Dynamic equilibrium, equal rates in both directions Biological membrane:
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Carrier proteins: Bind specific molecule & change shape Pass molecule through middle of protein
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Osmosis- diffusion of a water through a semi- permeable membrane Moves down concentration gradient e.g., Two sugar solutions of different concentrations separated by porous membrane which lets water through but not sugar What will happen?
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More concentrated to less concentrated Until concentration same on both sides: isotonic
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Concentration of solute less: solution is hypotonic. Concentration of solute greater: solution is hypertonic.
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Animal cells No cell walls Isotonic environment: Influx of water equals the efflux of water No change in cell shape
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Hypotonic solution: Water enters cell Bursts, or lyses Hypertonic solution: Water leaves cell Shriveled, or crenate
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Glomerular filtration
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Passive transport & facilitated diffusion do NOT require ATP
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DOES require the input of ATP Transport proteins AGAINST concentration gradient outside cell inside cell
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ATP ADP + P i + Energy
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nuclei mucus
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Membrane Permeability Cell membrane: selectively permeable 4 factors that determine permeability lipid solubility molecular size polarity charge 1 2 3 4
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Lipid solubility Most important factor Hydrophobic molecules Passively diffuse Hydrocarbons, carbon dioxide, & oxygen
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Molecular Size and Polarity Larger molecules, less permeable Lower kinetic energy Small pore sizes in the membrane Polar molecules hydrophilic, less permeable Very small, polar uncharged (water) molecules can diffuse - + Molecular Size Polarity
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Charge Charged molecules hydrophilic, less permeable Surrounded by coat of water (hydration shell), increases the size
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Rough and Smooth ER
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Digest food Autophagy Autolysis
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Rid body of toxic substances Contains enzymes that can oxidize various organic substances Liver cell
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Centriole pair Assemble microtubules Assist in cell division 9 clusters of microtubule triplets
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Figure 3.23c (c) Microtubules Hollow tubes of spherical protein subunits called tubulins 25 nm Tubulin subunits Microtubules appear as gold networks surrounding the cells’ pink nuclei in this photo.
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Cillia & Flagella- 9x2 arrangement 0.1 micrometer
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Cillia & Flagella- 9x2 arrangement
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Flagellum
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Flagellar Movement
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Ciliated Epithelium ciliated surface nuclei mucus
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Ciliary Movement
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Ameboid Movement Ex. WBC
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INQUIRY 1.Define isotonic, hypotonic, and hypertonic. 2.What % saline is a cell? 3.Distinguish between active and passive transport. 4.What is the function of: Mitochondria Nucleus Golgi apparatus Lysozome Ribosomes Smooth and rough ER Cellular Visions: The inner life of a cell (video) http://www.studiodaily.com/main/searchlist/6850.html
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