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The Cell

The Cell. Chapter 6. History of Cytology. Initial microscopes Robert Hooke Origin of term cell Antoni Van Leeuwenhoek First to visualize living cells Cell Theory developed by Schleiden, Schwann, and Virchow Every organism is composed of 1+ cells

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The Cell

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  1. The Cell Chapter 6

  2. History of Cytology • Initial microscopes • Robert Hooke • Origin of term cell • Antoni Van Leeuwenhoek • First to visualize living cells • Cell Theory developed by Schleiden, Schwann, and Virchow • Every organism is composed of 1+ cells • A cell is the simplest unit to demonstrate the properties of life • Cells arise only from previously existing cells

  3. Visible light is refracted (bent) through glass lenses Magnification is ratio of image size to real size Resolution is minimum distance 2 points can be separate and still distinguishable Light Microscopy

  4. Electron Microscope (EM) Scanning (SEM) Transmission (TEM) Details of cell surfaces, 3D image Details of internal cell structures • Uses a beam of electrons = higher resolution • Can’t use on living cells

  5. Similarities in All Living Cells • Plasma membrane: allows selective passage of molecules • Double layer of phospholipids • Variety of proteins spread throughout • Varies with cell location and function • Cytosol or cytoplasm: semisolid substance enclosed by the plasma membrane • Chromosome(s): carry genes as DNA • Ribosomes: tiny complexes that make proteins (genes direct)

  6. Cellular Classification • Prokaryotes- before nucleus • NO nucleus (nucleoid region) • NO organelles • Single, circular DNA • Smaller, less complex • E.g bacteria, archaea • Eukaryotes- true nucleus • Nucleus • Membrane bound organelles • DNA arranged on multiple chromosomes • Larger • E.gprotists, fungi, plants, animals

  7. The Simplicity of Cells • Many small cells advantaged over few large cells • As cells grow, volume increases faster than surface area • Ratio constrains size b/c limits amount of nutrients in and wastes out • Effects shapes and body plans too

  8. Eukaryotic Cell Types Plant Animal

  9. Genetic Control of the Cell • Nucleus is the control center that directs the cell • Enclosed by a double membrane called a nuclear envelope • Nuclear pores allow substances to enter and leave • Nuclear lamina protein filaments that maintain shape • Chromosomes are the structures that carry genetic info • Consists of chromatin, a protein and DNA structure that coils before cell division • Nucleolus is where rRNA is synthesized from DNA instructions • Form small and large subunits that exit the nuclear pores to form ribosomes in the cyoplasm

  10. Ribosomes • Use DNA to make proteins • Made of rRNA and protein complexes • Build proteins in 2 locations • Free ribosomes formed in cytosol • Proteins will remain/function in cytosol • Bound ribosomes are attached to endoplasmic reticulum or nuclear envelope • Make proteins that are shipped out of initial cell • Can change building location/type • Structurally identical

  11. Trafficking and Metabolism • Endomembrane system • Multiple responsibilities • Related through connections or vesicle transport • Endoplasmic reticulum • Separates internal compartment of ER from cytosol • Smooth ER lacks ribosomes • Synthesis lipids and carbs; detoxes alcohol and poisons • Detox induces proliferation = increase tolerance to drugs • Rough ER • Site of protein synthesis • Secrete proteins in vesicles that bud from membrane • Expands itself (makes own phospholipids)

  12. Golgi Apparatus • Modifies, stores, and sends products elsewhere • Cis = closest to Er • Receive vesicles from ER • Trans = opposite side • Ships products in vessels • Modified as move between two sides • Manufactures and refines products in stages

  13. Lysosomes • Made by rough ER and sent to golgi • Use hydrolytic enzymes to phagocytize food or damaged organelles • Best in acidic conditions • Decreased reaction if they break open • Can lead to cell destruction • Fuse with phagocytotic cells to break down polymers • E.g WBC’s attack and destroy bacteria • Autophagy recycles cell’s own materials • Continuous renewal of cell

  14. Vacuoles • Used for storage or transport of substances made by the ER • Contractile vacuoles removeexcess water from cell • Hydrolysis in plants and fungi b/c no lysosomes • Central vacuole transports solutes in plant cells; disposes of by-products • Pigmented to attract pollinators and signal poisonous

  15. Exchanging Energy • Mitochondria • Convert E to usable forms • Site of cellular respiration = synthesis of ATP • Number in a cell is related to membrane activity • 2 membranous layers • Innermost layered is folded to form cristae • Matrix is enclosed by inner and outer membranes • Chloroplasts • Contain chlorophyll or green pigment • Found in leaves and green plants • 2 membrane layers • Innermost is a group of interconnected sacs called thylakoids • Stacks are grana • Fluid outside thylakoids is the stroma

  16. Peroxisomes • Transfer H to O2 = H2O2 (hydrogen peroxide) • Break down fatty acids • Detoxify alcohol in liver • Don’t bud from ER, grow by incorporating proteins from cytosol and lipids

  17. Microtubules • Thickest fibers, made of dimers of tublin (α- and β) • A ring of 9 triplets comprise a centriole produced in a centrosome • Produce spindle fibers during cell division • Provides the mobility of cilia • Beat like an oar • A ring of 9 doubles and 2 singles produce a flagella

  18. Microfilaments • Solid rods of double twisted actin subunits • Sometimes mixed with myosin • Form structural networks • Allow dynein, a large motor protein to ‘walk’ • Interactions allow amoebas to move pseudopodia

  19. Intermediate Filaments • Made of different protein subunits including keratin • Maintain and bear tension • Remain after death • E.g keratinized skin

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