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Chapter 7 Cell Structures

Chapter 7 Cell Structures. Viruses - Considered nonliving in biology a. protein coat- capsid b. DNA/ RNA core. Prokaryotes vs Eukaryotes. *** Common features : - Cell membrane, cytoplasm, chromosomes, ribosomes. Contributions to Cytology :.

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Chapter 7 Cell Structures

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  1. Chapter 7Cell Structures

  2. Viruses- Considered nonliving in biologya. protein coat- capsidb. DNA/ RNA core

  3. Prokaryotes vs Eukaryotes *** Common features: - Cell membrane, cytoplasm, chromosomes, ribosomes

  4. Contributions to Cytology: • Robert Hooke (1665)- 1st to observe cells viewing a slice of cork/ coined to the term “cells” • Anton van Leeuwenhoek- 1st to view living cells (protists- “animalcules”) • M.J. Schleiden (1838)- plants composed of cells • Theodor Schwann (1839)- animals composed of cells • Robert Virchow (1858)- cells come from pre-existing cells

  5. Cell Theory • Schleiden, Schwann, and Virchow contributed to the cell theory • All living things are composed of cells • Cells are the basic unit of structure and function • Cells produced from pre-existing cells

  6. Eukaryotic Cell Structures • Domain Protista, Fungi, Plantae, and Animalia • Organelle“Little organ” • Specialized subunits within a cell that has a specific function • Usually enclosed within its own membrane *** NOTE: [*] =These structures contain DNA and are capable of replication

  7. a. Cell Membrane (Plasma membrane) • Double layer of protein and lipid around ALL cells • Separates the interior of a cell from the outside environment • Semi-permeable (selective)allows only certain substances to pass through

  8. Cell Membrane- Lipid Bilayer

  9. b. Cell Wall • Rigid, nonliving structure outside the cell membrane • Not present in Animals, but present in: 1. Plants & some protists(algae) cellulose- provides support to cells 2. Fungi chitin

  10. c. Nucleus • Double membrane bound organelle • Contains genetic material DNA • Known as the “control center of the cell”

  11. d. [*] Chromosome • Found within nucleus • Single DNA molecule • Segments represent different genes • Within eukaryotic cells: composed of DNA and proteins chromatin • Principal nuclear structure visible during cell division

  12. e. Nucleolus (i) • Small dense organelle within nucleus • Contains DNA, RNA, & protein • Within eukaryoticcells:assembleribosomes • Lily parenchyma cell (TEM x7,210) Note the large nucleus and nucleolus in the center of the cell

  13. f. Nuclear Membrane (Envelope) • Double membrane that surrounds the nucleus • Semi-permeable (selective) • Consists of protein-lipid molecules

  14. g. Cytoplasm (Cytosol) • All living material between the nuclear and plasma membrane • Semi-liquid substance that contains organelles Ex: ribosomes, chloroplasts, mitochondria

  15. h. Ribosomes • Small organelles composed of ribosomal RNA (rRNA) and proteins • 2 types:  1) Attached - Found on rough endoplasmic reticulum (RER) - Synthesizes extracellular proteins 2) Free - Found in cytoplasm - Synthesizes intracellular proteins ***[NOTE: Protein functions= a. enzymes/ b. structural parts]

  16. i. [*] Mitochondrion (ia) • Double membrane bound organelle • Produces ATPenergy for ALL cells • Contains own DNA and ribosomes • Site of cellular respiration (Krebs Cycle, respiratory chain, and oxidative phosphorylation)

  17. j. Endoplasmic Reticulum (ER) • Extensive system of membrane present in most eukaryotic cells • Material transported through these channels and canals • May connect to nuclear or cell membranes

  18. Cont. Endoplasmic Reticulum • 2 types: 1)Rough ER (RER) - Ribosomes attached to RER/ gives “rough” appearance - Synthesizes proteins and other materials for export 2) Smooth ER (SER) - No ribosomes attached - Synthesizes lipids and steroids - Metobolizes CHOs - Detoxify drugs and poisons

  19. k. Golgi Apparatus • Layer of flattened, disc-shaped sacs, tubules, and vesicles near nucleus of gland cells • Synthesizes cell secretions • Source of lysosomes

  20. l. Vacuoles • Membrane-bound sac • Transport raw materials to cell interior • Also transport wastes • Used for storage of water/ food • In plant cells: typically large and central

  21. Vacuole in Plant Cell

  22. m. Lysosomes • Double membrane bound sac containing hydrolytic enzymes - Hydrolytic (“water-splitting”) breakdown substances by adding H2O • Fuse with food vacuoles to digest contents • “Suicide bag”digest cytoplasm if membrane ruptures • - Present in white blood cells (WBC): leukocytes

  23. n. [*] Plastids • Cytoplasmic, often pigmented organelle in plant cells • Includes: 1. Amyloplast - Stores starch - Root and internal stem tissue- not exposed to light 2. Chromoplast - Contain variety of carotenoids yellow, red, orange pigments/ - Ex: carrots, tomatoes Amyloplasts in a potato cell Parenchyma cell containing chromoplasts: each red dot is a chromoplast that contains carotenoids

  24. Cont. Plastids 3. Chloroplast - Contain carotenoids and chlorophylls a, b, c, d, e - Contains DNA and ribosomes - Site for photosynthesis

  25. o. Cytoskeleton • Network of protein scaffolding or “skeleton” of the cytoplasm • Provides shape, organization, and movement • Consists of: 1. Microfilaments - Thinnest, solid protein tubules - Hold organelles in place - Enable cells to change shape 2. Intermediate Filaments

  26. Cont. Cytoskeleton 3. Microtubules - Thickest, hollow protein rods - Provides shape and support to cells - Serve as “tracks” for organelles to move on - Makes up the following: a. [*] Centrioles • Forms spindle pole during mitotic and meiotic cell division • Found in pairs at right angles near nucleus of animal cells • Have own DNA • Microtubules in triplets • Present ONLY in animal cells

  27. Cont. Microtubules b. Cilium (ia) • Short, numerous structures embedded in the surface of some eukaryotic cells • Arranged in rows (9 + 2 arrangement of microtubules) • Involved in locomotion and movement of substances across surface c. Flagellum (a) • Long, single threadlike organelle • Used in locomotion • 9 +2 arrangement of microtubules

  28. p. Kinetosome • Motion-controlling granules at base of flagella and cilia q. Fibrils • Protein molecules that form spindles during plant and cell division • Functions in specialized cells: a. musclecontraction b. nerve cells carry impulses

  29. r. Pinocytic Vesicle • Indentation in cell membrane which results in vacuole formation • 2 types: 1)Pinocytosis -“Cell drinking” - Intake of fluid by cell 2) Phagocytosis - “Cell eating” - Intake of solids - Function of WBC (leukocytes)

  30. s. Contractile Vacuole • Expels excess water in freshwater organisms placed in hypotonic environment/ ex: distilled water • Maintains appropriate concentrations of salts and other molecules

  31. Prokaryotic Cell Structures - Domain Archeabacteria and Eubacteria a. Plasmid small circular DNA separated from main chromosome b. Mesosomeinfolding of plasma membrane significant in copying DNA prior to division c. Nucleiodarea of cell containing the main chromosome

  32. Prokaryotic Replication

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