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Chapter4 sections+1 7
 

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  • Figure 4.1 E. coli O157:H7 bacteria ( red ) clustering on intestinal cells of a small child. This type of bacteria can cause a serious intestinal illness in people who eat foods contaminated with it.
  • Figure 4.2 Examples of cells. Each one of the cells pictured here is an individual organism; all are protists
  • Figure 4.3 Overview of the general organization of bacteria and eukaryotic cells. Archaeans are similar to bacteria in overall structure. The three examples are not drawn to the same scale.
  • Figure 4.3 Overview of the general organization of bacteria and eukaryotic cells. Archaeans are similar to bacteria in overall structure. The three examples are not drawn to the same scale.
  • Figure 4.3 Overview of the general organization of bacteria and eukaryotic cells. Archaeans are similar to bacteria in overall structure. The three examples are not drawn to the same scale.
  • Figure 4.4 Three examples of the surface-to-volume ratio. This physical relationship between increases in volume and surface area constrains cell size and shape.
  • Figure 4.5 Examples of microscopes. A) A compound light microscope. B) A transmission electron microscope (TEM).
  • Figure 4.5 Examples of microscopes. A) A compound light microscope. B) A transmission electron microscope (TEM).
  • Figure 4.6 Different microscopes reveal different characteristics of the same organism, a green alga ( Scenedesmus ).
  • Figure 4.7 Relative sizes. Below , the diameter of most cells is in the range of 1 to 100 micrometers. Right , converting among units of length; also see Units of Measure, Appendix IX.
  • Figure 4.9 At its most basic, a cell is a lipid bilayer bubble filled with fluid.
  • Figure 4.8 Cell membrane structure. A Organization of phospholipids in cell membranes. B–E Examples of common membrane proteins.
  • Figure 4.8 Cell membrane structure. A Organization of phospholipids in cell membranes. B–E Examples of common membrane proteins.
  • Figure 4.10 A sampling of bacteria ( this page ) and archaeans
  • Figure 4.10 A sampling of bacteria ( this page ) and archaeans
  • Figure 4.11 Generalized body plan of a bacterium or archaean.
  • Figure 4.12 A biofilm. A single species of bacteria, Bacillus subtilis , formed this biofilm. Note the distinct “neighborhoods.”
  • Figure 4.13 Transmission electron micrographs of eukaryotic cells. A Human white blood cell. B Photosynthetic cell from a blade of timothy grass.
  • Figure 4.14 The cell nucleus. TEM at right , nucleus of a mouse pancreas cell.
  • Figure 4.15 Nuclear pores. Each is an organized cluster of membrane proteins that selectively allows substances to cross the nuclear membrane.

Chapter4 sections+1 7 Chapter4 sections+1 7 Presentation Transcript

    • Chapter 4 Cell Structure (Sections 4.1 - 4.7)
    • 4.1 Food for Thought
    • Helpful intestinal bacteria make vitamins that mammals can’t, and they crowd out more dangerous germs
    • Escherichia coli is one of the most common intestinal bacteria of warm-blooded animals – only a few of the hundreds of types ( strains ) are harmful
    • E. coli O157:H7
    • E. coli O157:H7 makes a potent toxin that can severely damage the lining of the human intestine
    • Causes serious illness in people who eat contaminated foods
    • 4.2 What, Exactly, Is a Cell?
    • cell
      • The smallest unit that has the properties of life
    • Cells pictured are individual organisms (protists)
    • Traits Common to All Cells
    • Although cells differ in size, shape, and function, each starts out with a plasma membrane , cytoplasm , and a region of DNA (in eukaryotic cells, a nucleus )
    • plasma membrane
      • A cell’s outermost membrane
      • A lipid bilayer is the structural foundation of cell membranes, including organelle membranes
    • Key Terms
    • organelle
      • Structure that carries out a specialized metabolic function inside a cell
    • cytoplasm
      • Semifluid substance enclosed by a cell’s plasma membrane
    • nucleus
      • Organelle with two membranes that holds a eukaryotic cell’s DNA
    • Single Cells
    • Bacterial Cell
    • Bacteria are single-celled organisms
    • Archaeans are similar to bacteria in overall structure
    • Fig. 4.3a, p. 52
      plasma membrane
      A Bacterial cell
      cytoplasm
      DNA
    • Plant Cell
    • Fig. 4.3b, p. 52
      B Plant cell
      plasma membrane
      DNA in nucleus
      cytoplasm
    • Animal Cell
    • Fig. 4.3c, p. 52
      C Animal cell
      DNA in nucleus
      cytoplasm
      plasma membrane
    • Animation: Overview of Cells
    • Constraints on Cell Size
    • S urface-to-volume ratio limits cell size
    • If the cell gets too big, inward flow of nutrients and outward flow of wastes across the membrane will not be fast enough
    • surface-to-volume ratio
      • A relationship in which the volume of an object increases with the cube of the diameter, but surface area increases with the square of the diameter
    • Surface-to-Volume Ratio
    • The physical relationship between increases in volume and surface area constrains cell size and shape
    • Animation: Surface-to-Volume Ratio
    • Cell Theory
    • The cell is the structural and functional unit of all organisms
    • cell theory
      • Theory that all organisms consist of one or more cells, which are the basic unit of life
    • History of Cell Discovery
    • 1665: Antoni van Leeuwenhoek first observed “many very small animalcules”
    • Robert Hooke magnified a piece of thinly sliced cork and named the tiny compartments he observed “ cellae ”
    • 1820s: Robert Brown was first to identify a cell nucleus
    • Matthias Schleiden, hypothesized that a plant cell is an independent living unit even when it is part of a plant
    • Schleiden and Theodor Schwann concluded that the tissues of animals as well as plants are composed of cells
    • Cell Theory
    • Four generalizations constitute the cell theory :
      • 1. Every living organism consists of one or more cells
      • 2. A cell is the smallest unit of life, individually alive even as part of a multicelled organism
      • 3. All living cells come from division of preexisting cells
      • 4. Cells contain hereditary material, which they pass to their offspring during division
    • Key Concepts
    • What Is a Cell?
      • A cell is the smallest unit of life
      • Each has a plasma membrane that separates its interior from the exterior environment
      • A cell’s interior contains cytoplasm and DNA
    • 4.3 Spying on Cells
    • Most cells are far too small to see with the naked eye
    • We use different types of microscopes and techniques to reveal cells and their internal and external details
    • Types of Microscopes
    • Light microscopes
    • Phase-contrast microscopes
    • Fluorescence microscope
    • Electron microscopes
    • Transmission electron Microscopes
    • Scanning electron microscopes
    • Examples of Microscopes
    • Compound light microscope
    • Transmission electron microscope (TEM)
    • Fig. 4.5a, p. 54
      specimen
      prism that directs rays to ocular lens
      focusing knob
      illuminator
      condenser lens
      stage
      path of light rays (bottom to top) to eye
      ocular lens
      objective lenses
      light source (in base)
    • Fig. 4.5b, p. 54
      phosphor screen
      incoming electron beam
      condenser lens
      specimen on grid
      objective lens
      projective lens
    • Animation: How a Light Microscope Works
    • Different Views, Same Organism
      Fig. 4.6, p. 55
      A Light micrograph.
      B Light micrograph.
      C Fluorescence micrograph.
      D A transmission electron micrograph reveals fantastically detailed images of internal structures.
      E A scanning electron micro-graph shows surface details. SEMs may be artificially colored to highlight specific details.
      A reflected light microscope captures light reflected from specimens.
      A phase-contrast microscope yields high-contrast images of trans- parent specimens. Dark areas have taken up dye.
      This image shows fluorescent light emitted by chlorophyll molecules in the cells.
    • Relative Sizes
    • Measurements
    • Units of length:
      • 1 centimeter (cm) = 1/100 meter, or 0.4 inch
      • 1 millimeter (mm) = 1/1000 meter, or 0.04 inch
      • 1 micrometer ( μ m) = 1/1,000,000 meter, or 0.00004 inch
      • 1 nanometer (nm) = 1/1,000,000,000 meter, or 0.00000004 inch
      • 1 meter = 10 2 cm = 10 3 mm = 10 6 μ m = 10 9 nm
    • Key Concepts
    • Microscopes
      • Most cells are too small to see with the naked eye
      • We use different types of microscopes to reveal different details of their structure
    • Animation: How an Electron Microscope Works
    • 4.4 Membrane Structure and Function
    • A cell membrane functions as a selectively permeable barrier that separates an internal environment from an external one
    • Membranes of most cells can be described as a fluid mosaic of lipids (mainly phospholipids) and proteins
    • Lipids are organized as a lipid bilayer : a double layer of lipids in which the nonpolar tails of both layers are sandwiched between the polar heads
    • Key Terms
    • lipid bilayer
      • Structural foundation of cell membranes; double layer of lipids arranged tail-to-tail
    • fluid mosaic
      • Model of a cell membrane as a two-dimensional fluid of mixed composition
    • A Lipid Bilayer
    • Basic Cell
    • At its most basic, a cell is a lipid bilayer bubble filled with fluid
    • Membrane Proteins
    • Proteins associated with a membrane carry out most membrane functions
    • All membranes have transport proteins
    • Plasma membranes also have receptor proteins , adhesion proteins , enzymes, and recognition proteins
    • Key Terms
    • transport protein
      • Protein that passively or actively assists specific ions or molecules across a membrane
    • adhesion protein
      • Membrane protein that helps cells stick together in tissues
    • receptor protein
      • Binds to a particular substance outside of the cell
    • recognition protein
      • Tags a cell as belonging to self (one’s own body)
    • Membrane Proteins
    • Recognition and Receptor Proteins
    • Transport Proteins
    • Fig. 4.8b-e, p. 57
      Lipid Bilayer
      Cytoplasm
      Extracellular Fluid
      E This transport protein, an ATP synthase, makes ATP when hydrogen ions flow through its interior.
      B Recognition proteins such as this MHC molecule tag a cell as belonging to one’s own body.
      C Receptor proteins such as this B cell receptor bind substances outside the cell. B cell receptors help the body eliminate toxins and infectious agents such as bacteria.
      D Transport proteins bind to molecules on one side of the membrane, and release them on the other side. This one transports glucose.
    • Animation: Cell Membranes
    • Variations on the Model
    • Archaeans do not build phospholipids with fatty acids –instead, the tails of archaean phospholipids form covalent bonds with one another
    • Archaean membranes are far more rigid than those of bacteria or eukaryotes
    • Key Concepts
    • Cell Membranes
      • All cell membranes consist mainly of a lipid bilayer and different types of proteins
      • The proteins carry out various tasks, including control over which substances cross the membrane
    • Animation: Lipid Bilayer Organization
    • Animation: Fluid Mosaic Model
    • 4.5 Bacteria and Archaeans
    • Single-celled bacteria and archaeans are the smallest and most diverse forms of life:
      • The cytoplasm contains ribosomes and plasmids
      • A single, circular chromosome is located in a nucleoid
      • Many have a cell wall , flagella or pili
    • Key Terms
    • ribosome
      • Organelle of protein synthesis
    • plasmid
      • Small circle of DNA in some bacteria and archaeans
    • nucleoid
      • Region of cytoplasm where the DNA is concentrated inside a bacterium or archaean
    • Key Terms
    • flagellum
      • Long, slender cellular structure used for motility
    • pilus
      • A protein filament that projects from the surface of some bacterial cells – sex pilus
    • cell wall
      • Semi-rigid but permeable structure that surrounds the plasma membrane of some cells
    • Bacteria
    • Archaeans
    • Body Plan of Bacteria and Archaeans
    • Fig. 4.11, p. 58
      flagellum
      cytoplasm, with ribosomes
      DNA in nucleoid
      pilus
      plasma membrane
      cell wall
      capsule
    • Animation: Typical Prokaryotic Cell
    • Cell Walls
    • The cell wall of most archaeans consists of proteins
    • The wall of most bacteria consists of a polymer of peptides and polysaccharides
    • Sticky polysaccharides form a slime layer, or capsule, around the wall of many types of bacteria
    • Biofilms
    • Biofilms are shared living arrangements among bacteria and other microbial organisms
    • biofilm
      • Community of different types of microorganisms living within a shared mass of slime
      • May include bacteria, algae, fungi, protists, and archaeans
    • A Biofilm
    • A biofilm organizes itself into “neighborhoods,” each with a distinct microenvironment that stems from its location within the biofilm and species that inhabit it
    • Key Concepts
    • Bacteria and Archaea
      • Archaeans and bacteria have few internal membrane-enclosed compartments
      • In general, they are the smallest and structurally the simplest cells, but they are also the most numerous
    • 4.6 Introducing Eukaryotic Cells
    • All protists, fungi, plants, and animals are eukaryotes
    • Eukaryotic cells start out life with membrane-enclosed organelles, including a nucleus
    • Most eukaryotic cells contain an endomembrane system (ER, vesicles, and Golgi bodies), mitochondria, and a cytoskeleton
    • Components of Eukaryotic Cells
    • Animal and Plant Cells
    • Fig. 4.13, p. 60
      nucleus
      cell wall
      central vacuole
      vacuole
      plasma membrane
      chloroplast
      mitochondrion
    • 4.7 The Nucleus
    • The nucleus contains the cell’s genetic material (DNA)
    • In the nucleus, ribosome subunits are assembled in dense regions called nucleoli
    • The nucleus has a double-membraned nuclear envelope surrounding nucleoplasm
    • Key Terms
    • nucleolus
      • In a cell nucleus, a dense, irregularly shaped region where ribosomal subunits are assembled
    • nuclear envelope
      • A double membrane that constitutes the outer boundary of the nucleus
    • nucleoplasm
      • Viscous fluid enclosed by the nuclear envelope
    • The Nuclear Envelope
    • The nuclear membrane controls passage of certain molecules between the nucleus and the cytoplasm
    • Receptors and transporters stud both sides of the nuclear envelope; other proteins form nuclear pores
    • The outer bilayer of the double membrane is continuous with the membrane of the ER
    • The Nucleus
      Fig. 4.14, p. 61
      nucleoplasm
      nuclear envelope
      nuclear pore
      nucleolus
      ER
      cytoplasm
      DNA
    • Nuclear Pores
      Fig. 4.15, p. 61
      nuclear pore
      cytoplasm
      nuclear envelope (two lipid bilayers)
    • Animation: Nuclear Envelope