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Searchyahoocomsearchvide oylta0og7mdii1n3q4agalxnyoa

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Unformatted text preview: ilayer is asymmetrical • Regulates entry and exit of chemicals Outside of cell Hydrophilic region of protein Proteins Hydrophilic head Hydrophobic tail Phospholipid bilayer Hydrophobic regions of protein Cytoplasm (inside of cell) (b) Fluid mosaic model of membrane Mosaic Model Mosaic Model • http://video.search.yahoo.com/search/vide o;_ylt=A0oG7m.dIi1N3q4AGAlXNyoA? ei=UTF­8&p=fluid%20mosaic%20model %20of%20membrane %20structure&fr2=tab­web&fr=yfp­t­701­s The Nucleus The Nucleus • The ‘powerhouse’ of the cell, 5 µ m diameter • Contains the genetic material, DNA, in the form of chromosomes • Bordered by double membrane, nuclear envelope DNA molecule Proteins Chromatin fiber Chromosome Chromatin Packing in Eukaryotic Chromosome Chromosome Nucleosome DNA double helix (2 nm in diameter) Proteins DNA, the double helix Nucleosomes, or “beads on a string” (10-nm fiber) Chromatid (700 nm) 30-nm fiber Loops Scaffold 300-nm fiber Replicated chromosome (1,400 nm) 30-nm fiber Looped domains (300-nm fiber) Metaphase chromosome The Nucleus The Ribosomes Ribosomes • Protein­making organelles • Assembled in the cytoplasm • Membrane­bound ribosomes make proteins for secretion or membrane • Cytosol ribosomes make proteins that remain in the cytosol Computer model of a ribosome synthesizing a protein Computer Ribosome mRNA Protein Cytosol Endoplasmic reticulum (ER) Free ribosomes Bound ribosomes Large subunit Small subunit 0.5 µm TEM showing ER and ribosomes How genes in the nucleus control the cell control The Endomembrane System • Regulates protein traffic and performs metabolic functions 1. Nuclear Envelope 2. Endoplasmic reticulum 3. Golgi Apparatus 4. Lysosomes 5. Vacuoles Smooth ER Rough ER Nuclear envelope ER lumen Cisternae Ribosomes Transport vesicle Smooth ER Transitional ER Rough ER 200 nm The Endoplasmic Reticulum Smooth ER • Makes up small part of total ER, except in specialized cells • Site of lipid synthesis • Site of detoxification of lipid­soluble drugs Rough ER • Can produce new membrane • Produces proteins destined for other locations within the cell • Produces secretory proteins The Endoplasmic Reticulum • One of cell’s main manufactur...
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