Cells Structural and functional units of living organisms
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Transcript of Cells Structural and functional units of living organisms
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Cells
Structural and functional units of living organisms
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Eukaryotic (“true nucleus”) vs. Prokaryotic (“before nucleus”) cells
Proks
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Eukaryotic (“true nucleus”) vs. Prokaryotic (“before nucleus”) cells
Proks - nucleoid is not separated from cytoplasm by a membrane
Euks -
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Eukaryotic (“true nucleus”) vs. Prokaryotic (“before nucleus”) cells
Proks - nucleoid is not separated from cytoplasm by a membrane
Euks - nuclear material is enclosed in a double membrane - nuclear envelope
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Prokaryotic vs. Eukaryotic Cells
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Prokaryotic vs. Eukaryotic Cells
Changes from Proks to Euks:(1) DNA size and compactions
(2) Cell size and organization
(3) Early euk cells were endosymbiotic
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Prokaryotic vs. Eukaryotic Cells
Changes from Proks to Euks:(1) Euks have more DNA than proks so cells needed better ways to fold the DNA compactly into complexes (using proteins) so that the DNA was divided equally between daughter cells at cell division, complexes = chromosomes (chromatin)
(2) Euk cells larger so needed a better system of intracellular membranes, so development of double membrane around DNA (nucleus); membrane separated nuclear process of RNA synthesis from cytoplasmic process of protein synthesis
(3) Early euk cells, which were unable to perform photosynthesis or aerobic metabolism, enveloped aerobic/photosynthetic bacteria to form endosymbiotic species, some aerobic bacteria became mitochondria and some chloroplasts
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Development of Eukaryotic Cells
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Prokaryotic (bacterial) Cell
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Prokaryotic Cells
Two groups:Archaebacteria recently discovered
live in extreme environments (salt lakes, hot springs, deep in ocean)
Eubacteria most commonwell-studied (Escherichia coli/E. coli)inhabit soil, surface water, organisms
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Eukaryotic Cell
Animal cell
Plant cell
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Eukaryotic Cell
Plasma membrane
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Eukaryotic Cell
Plasma membrane
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Eukaryotic Cell
Endoplasmic Reticulum (ER)
Membrane-enclosed compartmentsExtends through cytoplasmFlattened branches = cisternae
Smooth ER (lipid biosynthesis, drug metabolism)
Rough ER (LOTS OF PROTEIN SYNTHESIS) -
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Eukaryotic Cell
Endoplasmic Reticulum (ER)
Membrane-enclosed compartmentsExtends through cytoplasmFlattened branches = cisternae
Smooth ER (lipid biosynthesis, drug metabolism) - Ribosome free
Rough ER (LOTS OF PROTEIN SYNTHESIS) - Ribosomes attached
ALSO free ribosomes - synthesize proteins that will remain in cytosol
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Eukaryotic Cell
Golgi Complex
Membrane-enclosed compartmentsExtends through cytoplasmFlattened branches = cisternae
Site of
Types of Modifications
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Eukaryotic Cell
Golgi Complex
Membrane-enclosed compartmentsExtends through cytoplasmFlattened branches = cisternae
Site of processing, packaging and targeting of proteins
Modifications - sulfate, carbohydrate, lipids, etc.Modification tags protein for its destination
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Eukaryotic Cell
Lysosomes
Animal cells only
Contain enzymes that digest
Enzymes kept inside by membrane
Lysosome pH -
Enzymes within lysosome act best at _____ pH
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Eukaryotic Cell
Lysosomes
Animal cells only
Contain enzymes that digest proteins, polysaccharides, nucleic acids, lipids
Enzymes kept inside by membrane
Lysosome pH - ATP-fueled proton pump keeps pH in lysosome at ~5.0 rather than 7.0 (in cytosol)
Enzymes within lysosome act best at lower pH
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Eukaryotic Cell
Peroxisomes
Purpose -
Example: H2O2
2H2O2 --> 2H2O + O2
Catalase
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Eukaryotic Cell
Peroxisomes
Purpose - take up reactive chemical species that could otherwise damage cell machinery
Example: H2O2
2H2O2 --> 2H2O + O2
Catalase at high concentration in peroxisome
Catalase
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Eukaryotic Cell
NucleusContains cellular DNA (some DNA in mitochondria and chloroplast)
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Eukaryotic CellNucleusChromosomes = 2 chromatids
Chromatin mass = 50% DNA, 50% histones
DNA of single human chromosome forms ~1,000,000 nucleosomes
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Eukaryotic CellMost cells (somatic cells) have 2 copies of each chromosome
Gametes, germline cells (egg and sperm) have only 1 copy of each chromosome
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Eukaryotic CellMitochondria
Diameter of ~1 µm (bacterial cells)100s-1000 per cellMetabolic cells have more mitochondriaMatrix has lots of enzymes and metabolic intermediatesHave their own DNA, RNA and ribosomesDescendants of aerobic bacteria??
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Eukaryotic Cell
CytoskeletonMeshwork through cytoplasmProvides structure and organization to cytoplasm and shape to cell
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Viruses = Parasites of Cell
Viruses
Replicate themselves in host cellsContain DNA or RNA surrounded by a capsid (protective coat)Outside host cell, virus is nonliving particle (virion)Inside host cell, virus is parasiteUses host cells’ machinery to make more virus particles
Turnip yellow mosaic virus (spheres)Tobacco mosaic virus (cylinders)Bacteriophage T4
HIV
Poliovirus
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Secretory cells of pancreas
Skeletal muscle cell
Sperm cells
Red blood cells
Human embryo at 2-cell stage