1 / 79

Chapter 6:

Chapter 6:. A Tour of the Cell. Key Concepts. 6.1 To study cells, biologists use microscopes and the tools of biochemistry. 6.2 Eukaryotic cells have internal membranes that compartmentalize their functions, and membrane bound organelles .

giselle-dodson
Download Presentation

Chapter 6:

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 6: A Tour of the Cell

  2. Key Concepts 6.1 To study cells, biologists use microscopes and the tools of biochemistry. 6.2 Eukaryotic cells have internal membranes that compartmentalize their functions, and membraneboundorganelles. 6.3 The Eukaryotic cell’s genetic instructions are found in the nucleus and carried out by the ribosomes. 6.4 The endomembrane system (ER) regulates protein traffic and performs metabolic function of the cell. 6.5 Mitochondria and chloroplasts change energy from one form to another. 6.6 The cytoskeleton is a network of fibers that organizes structures and activities inside the cell. 6.7 Extracellular components (outside the cell) and connections between cells (desmosomes, gapjunctions, tight junctions, and plasmodesmata) help coordinate cellular activities.

  3. Microscopy • The study of cells progressed with the invention of the microscope in 1590, and their improvement in the 17th century. • Light Microscope- earliest form, uses beam of light passed thru specimen and then thru glass lenses. • Electron Microscope- (1950’s) focuses a beam of electrons thru a specimen, or onto its surface. Highest magnification and resolution. • Transmission EM- (TEM) used to study the internal structures of a cell. • Scanning EM- (SEM) used to study the surface of a specimen.

  4. Light Microscope

  5. TEM

  6. SEM

  7. TECHNIQUE RESULTS 1 µm Cilia (a) Scanning electron microscopy (SEM) Fig. 6-4 Longitudinal section of cilium Cross section of cilium (b) Transmission electron microscopy (TEM) 1 µm

  8. Parameters in Microscopy • Magnification- the ratio of an objects image size to its real size • Resolution- a measure of the clarity of an object

  9. Staining Technique • The addition of certain chemical pigments allows for increased contrast between cell structures. • Makes structures easier to distinguish and study. • Examples- bromthymol blue, methyleneblue, crystal violet, safranin, malachitegreen, eosin

  10. TECHNIQUE RESULTS (a) Brightfield (unstained specimen) Fig. 6-3ab 50 µm (b) Brightfield (stained specimen)

  11. Cell Fractionation The goal of cell fractionation is to take cellsapart and separate major organelles from one another. The instrument used is a Centrifuge. The centrifuge spins test tubes holding mixtures of disrupted cells at high speeds. Uses centrifugal force. Enable scientists to prepare specific components of cells in bulk quantities to study their composition and structure.

  12. TECHNIQUE Fig. 6-5 Homogenization Tissue cells Homogenate 1,000 g (1,000 times the force of gravity) 10 min Differential centrifugation Supernatant poured into next tube 20,000 g 20 min 80,000 g 60 min Pellet rich in nuclei and cellular debris 150,000 g 3 hr Pellet rich in mitochondria (and chloro- plasts if cells are from a plant) Pellet rich in “microsomes” (pieces of plasma membranes and cells’ internal membranes) Pellet rich in ribosomes

  13. TECHNIQUE (cont.) 1,000 g (1,000 times the force of gravity) 10 min Fig. 6-5b Supernatant poured into next tube 20,000 g 20 min 80,000 g 60 min Pellet rich in nuclei and cellular debris 150,000 g 3 hr Pellet rich in mitochondria (and chloro-plasts if cells are from a plant) Pellet rich in “microsomes” (pieces of plasma membranes and cells’ internal membranes) Pellet rich in ribosomes

  14. Prokaryotic Usually single celled. Can form colonies. No nucleus or membrane-bound organelles. Genetic material localized (nucleoid) Ex. Bacteria Eukaryotic Kingdoms: Protista, Fungi, Plants, Animals. Nuclear membrane encloses DNA. Organelles that have membrane. Cells of Living Things

  15. Cell Size and Shape • Surface to Volume Ratio limits size of cells. Large cells require more raw materials. • V = cm3 S.A. = cm2 Restrictions on size and shape • Cells compartmentalize to increase SA/Vol, specialize rxn within, localize reactions where needed.

  16. Basic Aspects of Cell Structure and Function • Plasma membrane • Lipid bilayer • Proteins • Channels, transport, pumps, receptors • DNA-containing region • Cytoplasm

  17. Prokaryotic Cells Highly disorganized No membrane bound organelles Have a nucleoid (like a nucleus) Nucleoid contains genetic material (DNA) Have a plasma membrane Have cytosol inside the cell in which the organelles are found Have ribosomes Smaller than Eukaryotic cells Examples- Bacteria, Archae

  18. Typical Prokaryote (Bacterial) Cell

  19. Fimbriae Fig. 6-6 Nucleoid Ribosomes Plasma membrane Cell wall Bacterial chromosome Capsule 0.5 µm Flagella (a) A typical rod-shaped bacterium (b) A thin section through the bacterium Bacillus coagulans (TEM)

  20. Eukaryotic Cells • Have membrane bound organelles • Are very organized • Have a nucleus (DNA) • Surrounded by either a cell wall or a plasma membrane • Examples- plants, animals, fungi, protists (amoeba, paramecium,euglena)

  21. Defining Structures of Eukaryotic Cells A Plant Cell An Animal Cell

  22. Plant vs. Animal Cell

  23. Nuclear envelope ENDOPLASMIC RETICULUM (ER) NUCLEUS Nucleolus Rough ER Smooth ER Fig. 6-9a Flagellum Chromatin Centrosome Plasma membrane CYTOSKELETON: Microfilaments Intermediate filaments Microtubules Ribosomes Microvilli Golgi apparatus Peroxisome Mitochondrion Lysosome

  24. Rough endoplasmic reticulum Nuclear envelope Nucleolus NUCLEUS Chromatin Smooth endoplasmic reticulum Fig. 6-9b Ribosomes Central vacuole Golgi apparatus Microfilaments Intermediate filaments CYTO- SKELETON Microtubules Mitochondrion Peroxisome Chloroplast Plasma membrane Cell wall Plasmodesmata Wall of adjacent cell

  25. Structures in the Cell • The tiny organs found inside the cell are called organelles. • Each of these structures performs a specific function that allows the cell to survive.

  26. Major Cellular Components • Nucleus • Ribosomes • Endoplasmic reticulum • Smooth and Rough • Golgi body • Various vesicles • Mitochondria • Cytoskeleton

  27. Structures found in both Plant and Animal Cells • Plasma membrane • Nucleus • Chromatin • Nucleolus • Ribosomes • Endoplasmic Reticulum • Golgi Apparatus • Mitochondria • Peroxisomes • Cytoskeleton • Centrosomes

  28. Structures Associated with Animal Cells • Lysosomes • Centrioles • Flagella • Extracellular matrix • Tight Junctions • Desmosomes • Gap Junctions

  29. Structures Associated with Plant Cells • Central Vacuoles • Chloroplasts • Cell Wall • Plasmodesmata

  30. Components of the Nucleus • Nuclear envelope - Surrounds nucleus • Chromosome - One DNA molecule and associated proteins. Organized DNA. • Chromatin - DNA molecules and histone proteins. Condenses to form DNA. • Nucleolus - RNA and proteins that will be assembled into ribosomal subunits. Cells may have more than one.

  31. The Nuclear Envelope • Double - membrane system • Two lipid bilayers. 20-40 nm thick. • Surrounds chromatin/nucleoplasm • Pores allow exchange. Composed of about 100 proteins.

  32. Smallest, most numerous organelle. Composed of rRNA and proteins. Synthesized by nucleolus. Large and small subunits. Found free and bound to E.R. Differ only in what they are making. Catalyzes formation of peptide bonds. Ribosomes

  33. The Endomembrane System • Organelles in which lipids are assembled and proteins are produced and modified • Are in direct contact or send vesicles (membrane-bound sacs). • Occupy ½ of cell volume. • Nuclear envelope, endoplasmic reticulum, golgi apparatus, lysosomes, vacuole

  34. The Endoplasmic Reticulum • Network of tubes and sacs that are continuous with nuclear membrane. Most extensive mem. Sys. • Rough (ribosome studded) and Smooth. • Rough: production of secretory proteins. Signal sequence on polypeptide instructs ribosome to attach to ER. • Smooth: Lipids production, CH2O metabolism, storage of ions, detoxification of drugs/alcohol

  35. Endoplasmic Reticulum

  36. Cytosol Endoplasmic reticulum (ER) Fig. 6-11 Free ribosomes Bound ribosomes Large subunit Small subunit 0.5 µm Diagram of a ribosome TEM showing ER and ribosomes

  37. Nucleus 1 µm Nucleolus Chromatin Fig. 6-10 Nuclear envelope: Inner membrane Outer membrane Nuclear pore Pore complex Rough ER Surface of nuclear envelope Ribosome 1 µm 0.25 µm Close-up of nuclear envelope Pore complexes (TEM) Nuclear lamina (TEM)

  38. Smooth ER Nuclear envelope Rough ER Fig. 6-12 ER lumen Cisternae Transitional ER Ribosomes Transport vesicle 200 nm Rough ER Smooth ER

  39. Nucleus Fig. 6-16-1 Rough ER Smooth ER Plasma membrane

  40. Nucleus Fig. 6-16-2 Rough ER Smooth ER cis Golgi Plasma membrane trans Golgi

  41. Nucleus Fig. 6-16-3 Rough ER Smooth ER cis Golgi Plasma membrane trans Golgi

  42. Golgi Bodies Trans (exit) face • Enzymatic finishes on proteins and lipids, and packaging in vesicles. • Polarity of cisternae. • Forms glycolipids, glycoproteins, • Products of Golgi leave as vessicles. From one cisternae to another or out of cell. Cis (forming) face

  43. Lysosomes • Membrane-boundorganelle that contains hydrolytic enzymes responsible for the digestion of macromolecules, autolysis, intracellular digestion. • Dead cells no longer able to maintain H+ gradient (use H+ pump) so organelle breaks down releasing contents. • Made by ER and Golgi.

  44. Lysosome Function andProduction

  45. From Production to Export

  46. Storage of water or ions, pigments, hold food, pump out water. Are larger than vesicles formed from golgi/E.R. In plants is enclosed by Tonoplast (membrane) and provides cell with hydrostatic pressure Vacuoles

  47. Peroxisomes • Contain enzymes (catalase) that break down H2O2 formed during metabolism of alcohols, F.A.’s. • Specialized forms [glyoxysome] found in seeds and function during germination.

  48. Mitochondria • Production of ATP • Double-membrane system • Two distinct compartments • Have their own DNA. Maternal in origin. • Divide on their own, independent of cell. • Have ribosomes, produce enzymes necessary for ATP production.

  49. Chloroplast • Found in photosynthetic eukaryotes • Two outer membranes • Semifluid stroma; site of carbon fixation. • Inner thylakoid membrane system; converts l.e. into c.e. • Photosynthetic pigments found in other plastids.

  50. Cytoskeleton • Protein fibers that support and give shape to a cell, involved in organelle movement throughout cell, chromosome movement during cell division and large cell movements (cell motility and cytokinesis) • 3 Groups of Fibers classified according to size: • Mircrotubules (thickest) • Intermediated filaments (middle sized) • Microfilaments (thinnest)

More Related