Organization of the Cell

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Organization of the Cell
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Cell Theory

• Cells are the basic living units of organization
  and function
• All cells come from other cells
• Work of Schleiden, Schwann, and Virchow
  contributed to this theory
• Each cell is a microcosm of life

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• Biological Size and Cell Diversity

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• Cell surface area-to-volume ratio
• Plasma membrane must be large enough relative to
  cell volume to regulate passage of materials
• Volume increases faster than surface area so
  cells must divide
• Cell size and shape related to function

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• Cell Surface Area-to-Volume Ratio

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• Microscopes
• Light microscope, referred to as compound
  microscope, used by most students
• Two features determine how clearly an object is
  viewed
• Magnification
• Resolution
• Light microscope has 500 times more resolution
  than human eye

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• Electron microscope
• Developed in the 1950s
• Allows study of the ultrastructure of cells
• 10,000 times more resolution than human eye

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• Types of electron microscope
• Transmission electron microscope TEM
• Used to view internal cell structures
• Scanning electron microscope SEM
• Produces 3-D picture of cell surface
• Cant be used to view living cells

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• Comparing light and electron microscopy

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• Cell fractionation
• Used to determine isolate tell function of
  organelles
• Cells broken apart and the resulting cell extract
  spun in a centrifuge
• Centrifugal force separates extract
• Pellet heavier cell organelles
• Supernatant liquid poured off

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• Cell fractionation

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• Prokaryotic
• Bacteria and Archaea (ancient bacteria)
• DNA not enclosed in a nucleus
• Eukaryotic
• All other known organisms
• Highly organized membrane-enclosed organelles
• Cytoplasm
• Nucleoplasm

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• Functions of cell or plasma membranes
• Divide cell into compartments, allowing for
  specialized activities
• Interacting membranes form endomembrane system
• Vesicles transport materials between compartments
  (ER ? Golgi, Golgi ? plasma membrane)

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• Diagram ofa plant cell

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• Diagram ofan animal cell

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• The cell nucleus
• Contains DNA
• Bounded by
• Nuclear envelope
• Double membrane perforated with nuclear pores
• DNA forms chromatin, which is organized into
  chromosomes
• Nucleolus
• RNA synthesis and ribosome assembly

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• The cellnucleus

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• Endoplasmic reticulum (ER)
• Network of folded internal membranes in the
  cytosol
• Connected to Nuclear envelope
• Smooth ER
• Site of lipid synthesis
• Site of detoxifying enzymes
• Detoxifies drugs alcohol
• Stores Ca in muscle cells
• Rough ER
• Ribosomes on surface manufacture secretory
  proteins
• Proteins may be moved into the ER lumen (interior)

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• Endoplasmicreticulum (ER)

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• Golgi complex
• Cisternae that process, sort, and modify proteins
  
• In animal cells, Golgi complex also manufactures
  lysosomes
• Glycoproteins
• Transported to the cis face (receiving side)
• Golgi modifies carbohydrates and lipids and
  packages into vesicles that pinch off the trans
  face (shipping side)

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• Golgi complex

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• Lysosomes break down worn-out cell structures,
  bacteria, and other substances
• Responsible for cell death recycling
• Peroxisomes
• Involved in lipid metabolism and detoxification
• Contain enzymes (catalase) that produce and
  degrade hydrogen peroxide H2O2 ? H2O O2

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• Lysosomes

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• Mitochondria
• Sites of aerobic respiration
• Organelles enclosed by a double membrane
• Has its own genome
• Place important role in apoptosis
• Cristae (internal folds) and matrix (innermost
  space) contain enzymes for aerobic respiration
• Nutrients broken down and energy packaged in ATP
• Carbon dioxide and water by-products

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• Mitochondria

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• Chloroplasts
• Plastids that carry out photosynthesis
• Inner membrane of chloroplast encloses the stroma
  gel-like liquid)
• Contains stacks of interconnected sacs called
  thylakoids
• Stack of thylakoids called grana
• During photosynthesis, chlorophyll traps light
  energy (sunlight)
• Energy converted to chemical energy in ATP

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• Chloroplast

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• Cellular respiration and photosynthesis

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• Cytoskeleton
• Internal framework made of
• Microtubules - tubulin
• Microfilaments - actin
• Intermediate filaments - keratin
• Provides structural support
• Involved with transport of materials in the cell
• Make up cilia, flagella, and centrioles

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• TheCytoskeleton

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• Cilia and flagella
• Thin, movable structures that project from cell
  surface
• Function in movement
• Microtubles anchored in cell by basal body

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• Structureof cilia

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• Glycocalyx
• Cell coat formed by polysaccarides extending
  from plasma membrane
• Many animal cells also surrounded by an
  extracellular matrix (ECM)
• Most bacteria, fungi, and plant cell walls made
  of carbohydrates

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• Extracellular matrix

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• Plantcell walls

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