Biology 1020 Lecture 7 Cell Structure 2

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  1. Eukaryotic cell structure: endomembrane system
    • Membranes within the cell, continuous or connected via transfer by vesicles (sacs made of membrane)
    • - Nuclear envelope
    • - Endoplasmic reticulum
    • - Golgi apparatus
    • - Lysosomes
    • - Vesicles and vacuoles
  2. Eukaryotic cell structure: endoplasmic reticulum
    • - 50% of the total membrane
    • - continuous with the nuclear envelop
    • - Lumen: Space inside ER
    • - Smoothe ER - Lacks ribosomes
    • - Rough ER - with ribosomes
  3. Smooth ER
    • Synthesizes lipids: eg. phospholipids and steriods
    • metabolizes carbohydrates
    • Detoxifies poison (poisons induce production of smooth ER - tolerance). Increasd smooth ER often in the liver
    • Stores calcium (especially in muscle cells)
  4. Rough ER
    • Modifies proteins (add carbohydrates --> glycoproteins) (insulin-pancreatic RER)
    • Distributes transport vesicles
    • Produces membranes
  5. Golgi Apparatus
    • Flattened membranous sacs - cisternae
    • Cisternae are not connected. (Like pita bread stacked on top of each other)
    • Cis face ("receiving"side of Golgi apparatus)
    • Trans face ("shipping"side of Golgi apparatus)
    • Modifies products of the ER
    • Manufactures macromolecules, eg. glycolipids
    • Encloses materials in transport vesicles. Some vesicles rejoin Golgi for further modification
  6. Secretory molecule/membrane protein production
    • Protein ribosome into ER lumen (fold into shape)
    • Carbohydrates attached to protein (and with glycolipids from smooth ER).
    • Wrapped in membrane - transport vesicles
    • Cis face of Golgi
    • Vesicle forms/joins cis cisternae
    • further modification
    • Move towards Trans face
    • Leave trans face of golgi
    • Golgi vesicles go to membrane
    • Fuses with plasma membrane.
    • Continuous with inside face of plasma membrane
    • glycoproteins/glycolipids on outside of plasma membrane.
  7. Peroxisomes
    • Single membrane
    • Break down fatty acids, detoxification
    • H ions from substrates + oxygen --> hydrogen peroxide --> water
    • Glyoxysomes in plant seeds contain enzymes that convert fatty acids into sugar
  8. Mitochondria
    • Inner membrane separates two components: intermembrane space and mitochondrial matrix
    • Circular DNA is associated with inner membrane
    • Maternal (inherited from the mother)
    • Ribosomes in the matrix make proteins for the mitochondria: e.g. some steps of cellular respiration
    • Enzymes on the inner membrane - cristae increase surface area for the enzymes
    • Mitochondria fuse, divide
    • Number varies by cell/tissue type, in response to factors
  9. Number of mitochondria varies by species and by tissue
    • Red muscle has many mitochondria - steady oxygen consuming activity
    • White muscle has fewer mitochondria - burst activity that doesn't use oxygen
  10. Vacuoles
    • Large membrane (from ER and Golgi) bound vesicles
    • They each have a specific function such as storage, transport, digestion, etc.
    • Food Vacuoles are formed by phagocytosis
    • Contractile vacuoles, in many freshwater protists, pump excess water out of cells
    • Central vacuoles, found in many mature plant cells - Hold organic compounds and water
  11. Structures unique to plant cells and animal cells
    • Plant
    • - Chloroplasts
    • - Central Vacuole
    • - Cell wall
    • - Plasmodesmata

    • Animal
    • - Lysosomes
    • - Centrosomes
    • - Flagella
  12. Animal Cell structure: Lysosomes
    • Membranous sac of hydrolytic enzymes-digests macromolecules (low pH)
    • Bud from the endomembrane system (rough ER --> Golgi)
    • Involved Phagocytosis and Autophagy
  13. Lysosome: Phagocytosis
    • Cell engulfs and digests material (cell/food particles) that was outside of the cell --> Food vacuole
    • - Lysosome fuses with food vacuole
    • Released acid/enzyme digest materials
  14. Lysosomes: Autophagy
    Cell digests and recycles own organelles and macromolecules within cell
  15. Plant Cell Structure: Cell Wall
    • Extracellular: outside the cell
    • Synthesized by the cell
    • Protects cell, maintain its shape
    • Prevents excessive uptake of water

    • Composition: Cellulose micro fibers embedded in other polysaccharides and protein matrix
    • Wall of adjacent cells separated by thick polysaccharide - MIDDLE LAMELLA
  16. 1° (primary) cell wall
    Secreted first in a young plant: relatively thin and flexible
  17. Secondary Cell Wall
    • This wall is between the plasma membrane and the primary cell wall
    • several layers, strong and durable. Ex. Wood
  18. Chloroplasts
    • Sites of photosynthesis in plants and algae
    • Contain chlorophyll, enzymes, and other molecules for photosynthesis
    • Inner outer, thylakoid membranes
    • Inter membrane space between inner and outer membranes
    • Thylakoid membrane: Flattened connected sacs stacked to form grana
    • Stroma: Fluid outside thylakoid contains DNA and ribosomes

    Number of chloroplasts increases as a plant leaf grows
  19. Chloroplasts and mitochondria share several features
    • External, internal membrane (not endo membrane system)
    • Proteins made by free ribosomes within them
    • Independent DNA replication within the cell
  20. Evolution of eukaryotic cells
    * After oxygen production by photosynthetic prokaryotes ~2.1 billion YBP
  21. Endosymbiotic theory
    • Hypothesis of endosymbiosis --> Cell lives within host cell/host organism
    • Mitchondria/chloroplast evolved from small prokaryotes living within a larger host
    • As undigesteded prey or a parasite
    • Became interdependent --> became single organism
    • Mitochondria likely evolved before chloroplast
  22. Endosymbiotic theory: formation of the nucleus and endomembranes
    Infolding of plasma membrane to form nuclear membrane and ER
  23. Endosymbiotic theory: mitochondria from aerobic heterotrophic prokaryote
    • Engulf an aerobic prokaryote
    • Host able to use rising oxygen as a benefit in metabolism
  24. Endosymbiotic theory: Chloroplast from photosynthetic prokaryote
    • Host uses nutrients from photosynthesis of the endosymiont - cyanobacterium
    • Photosynthetic prokaryote --> Ancestral photosynthetic eukaryote
  25. Evidence for endosymbiotic theory
    • Similar characteristics between mitochondria/chloroplasts and prokaryotes
    • Membranes
    • Enzymes
    • Transport systems
    • Circular DNA --> Make protein in them
    • Divide by a similar process
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Biology 1020 Lecture 7 Cell Structure 2
2013-10-05 02:14:03
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