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Cell Structure and Function Chapter 3
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The Cell--Considerations Basic unit of life Protection and support Movement Communication Metabolism and energy release Inheritance
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Cell Theory All living things are made up of cell(s) Cells are smallest living unit of structure and function for all organisms All cells arise from preexisting cells (No spontaneous generation)
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Why Are Cell So Small?
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Sizes of living things
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Prokaryotes vs Eukaryotes Prokaryotes –“Before nucleus” –DNA in nucleoid region –Ribosomes –Cell membrane –No membrane–bound organelles Eukaryotes –“True nucleus” –DNA in double membrane bound nucleus –Ribosomes –Cell membrane –Membrane –bound organelles
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Typical Bacterium---A Prokaryote
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Typical Animal Cell-A Eukaryote
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Plasma Membrane
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Animal cell anatomy
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Plant cell anatomy
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Nucleus--The Brains of the Cell
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Nucleus DNA dispersed throughout Consists of : –Nuclear envelope: Separates nucleus from cytoplasm and regulates movement of materials in and out –Chromatin: Condenses to form chromosomes during cell division –Nucleolus: Assembly site of large and small ribosomal units
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Ribosomes Sites of protein synthesis Composed of a large and small subunit Types –Free –Attached to endoplasmic reticulum
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Composition of eukaryotic and prokaryotic ribosomes
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Cryoelectron microscopy–based image of the E. coli ribosome at ~25 Å resolution. Mol. Biol. Gene, Fig. 14-21
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The Endomembrane System Nuclear envelope Endoplasmic reticulum Golgi apparatus Vesicles
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Endoplasmic Reticulum Types –Rough Attached ribosomes Proteins produced and modified –Smooth No attached ribosomes Manufacture lipids Cisternae or Lumen: Interior spaces isolated from rest of cytoplasm
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Golgi Apparatus—Traffic Cop Modification, packaging, distribution of proteins and lipids for secretion or internal use Flattened membrane sacs stacked on each other
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Function of Golgi Apparatus
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Action of Lysosomes
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Peroxisomes and Proteasomes Peroxisomes –Smaller than lysosomes –Contain enzymes to break down fatty and amino acids –Hydrogen peroxide is a by-product of breakdown Proteasomes –Consist of large protein complexes –Include several enzymes that break down and recycle proteins in cell
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Energy Management Organelles Mitochondria –Aerobic Respiration Chloroplasts –Photosynthesis
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Circle of Life Carbon compounds, O 2 CO 2, H 2 O Respiration Photosynthesis Energy Mitochondria Chloroplasts Complex>>Simple
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Mitochondria—Powerhouse of the Cell In all eukaryotes Major site of ATP synthesis Membranes –Outer –Cristae: Infoldings of inner membrane Matrix: Substance located in space formed by inner membrane
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Chloroplast
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Animal cell anatomy
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Plant cell anatomy
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The Cytoskeleton Function: –Maintenance of cells shape –Movement within cytoplasm –Cell movement –Intracellular communication? Three components –Actin filaments –Microtubules –Intermediate filaments
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FUNCTION: CYTOSKELETON= complex network of filamentous proteins extending throughout the cytoplasm Three types of filaments: Microtubules Microfilaments Intermediate Filaments Cell shape Motility: crawling, chemokinesis chemotaxis endo- and exo-cytosis) Anchoring of organelles and cellular structures Organelle movement Cell polarity Tensile strength Chromosome movement
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helical structure, diameter ~ 7 nm EX. intestinal microvilli ACTIN FILAMENTS
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MICROFILAMENTS ACTIN STRUCTURES IN CELLS: MICROVILLI STRESS FIBRES FOCAL ADHESIONS LAMELLIPODIA FILOPODIA (or MICROSPIKES CONTRACTILE RING (cell division)
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hollow cyllinders, diameter ~ 25 nm, emanating from the MTOC
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Microtubule structure Made of and β Tubulin
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rope-like fibres, diameter ~ 10 nm, nuclear, cytoplasmic, connecting cell-cell junctions
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Structure of intermediate filaments
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micro- tubules micro- filaments intermediate filaments Cytoskeleton Elements
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Centrioles
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In specialized zone near nucleus: Centrosome Each unit consists of microtubules Before cell division, centrioles divide, move to ends of cell and become spindle fibers
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Cilia and flagella Cilia (small and numerous) and flagella (large and single) –9 + 2 pattern of microtubules – Iinvolved in cell movement. –Each has a basal body at its base. Plant cells lack centrioles
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Structure of a flagellum or cilium
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Prokaryotes vs Eukaryotes Prokaryotes –“Before nucleus” –DNA in nucleoid region –Ribosomes –Cell membrane –No membrane–bound organelles Eukaryotes –“True nucleus” –DNA in double membrane bound nucleus –Ribosomes –Cell membrane –Membrane –bound organelles
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Evolution of the eukaryotic cell- Endosymbiotic Hypothesis
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SUMMARY Cell Theory Physics of Cell Size Eukaryotes –Nucleus –Membrane Bound Organelles ER Golgi Vesicles, ex. Lysosomes –Energy Management Organelles –Cytoskeleton –Prokaryotes –Endosymbiosis
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