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  • Figure 4.16 Endomembrane system, where many proteins are modified and lipids are built. These molecules are sorted and shipped to cellular destinations or to the plasma membrane for export.
  • Figure 4.16 Endomembrane system, where many proteins are modified and lipids are built. These molecules are sorted and shipped to cellular destinations or to the plasma membrane for export.
  • Figure 4.17 The mitochondrion. This organelle specializes in producing large quantities of ATP.
  • Figure 4.17 The mitochondrion. This organelle specializes in producing large quantities of ATP.
  • Figure 4.17 The mitochondrion. This organelle specializes in producing large quantities of ATP.
  • Figure 4.18 The chloroplast, a defining character of photosynthetic eukaryotic cells. Bottom , transmission electron micrograph of a chloroplast from a tobacco leaf ( Nicotiana tabacum ). The lighter patches are nucleoids where the chloroplast’s own DNA is stored.
  • Figure 4.18 The chloroplast, a defining character of photosynthetic eukaryotic cells. Bottom , transmission electron micrograph of a chloroplast from a tobacco leaf ( Nicotiana tabacum ). The lighter patches are nucleoids where the chloroplast’s own DNA is stored.
  • Figure 4.18 The chloroplast, a defining character of photosynthetic eukaryotic cells. Bottom , transmission electron micrograph of a chloroplast from a tobacco leaf ( Nicotiana tabacum ). The lighter patches are nucleoids where the chloroplast’s own DNA is stored.
  • Figure 4.19 Cytoskeletal elements. Below , a fluorescence micrograph shows microtubules ( yellow ) and actin microfilaments ( blue ) in the growing end of a nerve cell. These cytoskeletal elements support and guide the cell’s lengthening.
  • Figure 4.20 Motor proteins. Here, kinesin ( tan ) drags a pink vesicle as it inches along a microtubule.
  • Figure 4.21 Examples of motile structures in cells. A Flagellum of a human sperm, which is about to penetrate an egg. B A predatory amoeba ( Chaos carolinense ) extending two pseudopods around its hapless meal: a single-celled green alga ( Pandorina ).
  • Figure 4.22 Mechanism of movement of eukaryotic flagella and cilia.
  • Figure 4.22 Mechanism of movement of eukaryotic flagella and cilia.
  • Figure 4.21 Examples of motile structures in cells. A Flagellum of a human sperm, which is about to penetrate an egg. B A predatory amoeba ( Chaos carolinense ) extending two pseudopods around its hapless meal: a single-celled green alga ( Pandorina ).
  • Figure 4.23 A plant ECM. Section through a plant leaf showing cuticle, a protective covering of deposits secreted by living cells.
  • Figure 4.24 Some characteristics of plant cell walls.
  • Figure 4.24 Some characteristics of plant cell walls.
  • Figure 4.25 Three types of cell junctions in animal tissues: tight junctions, gap junctions, and adhering junctions. In the micrograph above , a profusion of tight junctions ( green ) seals abutting surfaces of kidney cell membranes and forms a waterproof tissue. The DNA in each cell nucleus appears red .
  • Figure 4.26 Organelles and structures typical of A plant cells and B animal cells.
  • Figure 4.26 Organelles and structures typical of A plant cells and B animal cells.

Chapter4 sections+8 13 Chapter4 sections+8 13 Presentation Transcript

    • Chapter 4 Cell Structure (Sections 4.8 - 4.13)
    • 4.8 The Endomembrane System
    • The endomembrane system includes rough and smooth endoplasmic reticulum ( ER ), vesicles , and Golgi bodies
    • This system makes and modifies lipids and proteins; it also recycles and disposes of molecules and particles
    • endomembrane system
      • Series of interacting organelles (endoplasmic reticulum, Golgi bodies, vesicles) between nucleus and plasma membrane; produces lipids, proteins
    • The Endomembrane System
    • p. 62
      Stepped Art
      The Endomembrane System
      Makes lipids, breaks down carbohydrates and fats, inactivates toxins
      Smooth ER
      Finishes, sorts, ships lipids, enzymes, and proteins
      Golgi Body
      Modifies proteins made by ribosomes attached to it
      Rough ER
      Digests, recycles materials
      Lysosome
    • Endoplasmic Reticulum
    • endoplasmic reticulum (ER)
      • Organelle that is a continuous system of sacs and tubes
      • An extension of the nuclear envelope
      • Site where many new polypeptide chains are modified
      • Rough ER is studded with ribosomes that make polypeptides that enter the ER as they are assembled
      • Smooth ER has no ribosomes: Enzymes assemble lipids that form cell membranes, and break down substances
    • A Variety of Vesicles
    • Small, membrane-enclosed, saclike vesicles form in a variety of types, either on their own or by budding
    • Many vesicles transport substances from one organelle to another, including endocytic vesicles and exocytic vesicles
    • Other vesicles include peroxisomes , lysosomes , and vacuoles (including central vacuoles )
    • Key Terms
    • vesicle
      • Small, membrane-enclosed, saclike organelle; different kinds store, transport, or degrade their contents
    • lysosome
      • Enzyme-filled vesicle that functions in intracellular digestion
    • peroxisome
      • Enzyme-filled vesicle that breaks down amino acids, fatty acids, and toxic substances
    • Key Terms
    • vacuole
      • A fluid-filled organelle that isolates or disposes of waste, debris, or toxic materials
    • central vacuole
      • Fluid-filled vesicle in many plant cells
    • Golgi Bodies
    • Enzymes in a Golgi body finish proteins and lipids that are delivered by vesicles from the ER
    • Golgi body
      • Modifies polypeptides and lipids; a ttaches phosphate groups or oligosaccharides, and cuts certain polypeptides
      • Sorts and packages the finished products into vesicles that carry them to lysosomes or to the plasma membrane
    • Functions of the Endomembrane System
      Fig. 4.16.1,3, p. 62
      polypeptide
      ribosome attached to ER
      vesicle budding from ER
      RNA
      nucleus
      Vesicles Vesicles that bud from the rough ER carry some of the new proteins to Golgi bodies. Other proteins migrate through the interior of the rough ER, and end up in the smooth ER.
      3
      Rough ER Some of the RNA in the cytoplasm is translated into polypeptide chains by ribosomes attached to the rough ER. The chains enter the rough ER, where they are modified into final form.
      1
    • Functions of the Endomembrane System (cont.)
      Fig. 4.16.2,4,5, p. 62
      protein in smooth ER
      Smooth ER Some proteins from the rough ER are packaged into new vesicles and shipped to Golgi bodies. Others become enzymes of the smooth ER. These enzymes assemble lipids and inactivate toxins.
      2
      Golgi body Proteins arriving in vesicles from the ER are modified into final form and sorted. New vesicles carry them to the plasma membrane or to lysosomes.
      4
      Plasma membrane A vesicle’s membrane fuses with the plasma membrane, so the contents of the vesicle are released to the exterior of the cell.
      5
    • Animation: The Endomembrane System
    • 4.9 Mitochondria and Plastids
    • Mitochondria make ATP by breaking down organic compounds in the oxygen-requiring pathway of aerobic respiration
    • Chloroplasts are plastids that produce sugars by photosynthesis
    • Function of Mitochondria
    • mitochondrion
      • Double-membraned organelle that produces ATP by aerobic respiration in eukaryotes
    • During aerobic respiration, hydrogen ions accumulate between the two membranes
    • The buildup causes the ions to flow across the inner mitochondrial membrane, through membrane transport proteins that drive the formation of ATP
    • Mitochondrion
      Fig. 4.17a, p. 64
      inner compartment
      outer membrane
      outer compartment
      inner membrane
    • Fig. 4.17b, p. 64
      Mitochondrion
    • Fig. 4.17c, p. 64
      Energy powerhouse; produces many ATP by aerobic respiration
      Mitochondrion
    • Animation: Structure of a Mitochondrion
    • Origins of Mitochondria
    • Theory of endosymbiosis: Mitochondria evolved from aerobic bacteria that took up permanent residence inside a host cell
      • Resemble bacteria in size, form, and biochemistry
      • Have their own DNA, which is similar to bacterial DNA
      • Divide independently of the cell, and have their own ribosomes
    • Chloroplasts and Other Plastids
    • plastid
      • An organelle that functions in photosynthesis or storage, e.g. chloroplast, amyloplast
    • chloroplast
      • Organelle of photosynthesis in the cells of plants and many protists
    • Chloroplast Structure
    • Two outer membranes enclose a semifluid interior (stroma) that contains enzymes and chloroplast DNA
    • In the stroma, a highly folded stack of membrane (grana/granum ) forms a single, continuous compartment
    • Photosynthesis takes place at the thylakoid membrane, which incorporates pigments such as chlorophylls, which are green
    • Photosynthesis
    • Chlorophylls and other molecules in the thylakoid membrane use the energy in sunlight to synthesize ATP
    • ATP is used in the stroma to build carbohydrates from carbon dioxide and water
    • Chloroplasts
      Fig. 4.18a, p. 65
      Chloroplast Specializes in photosynthesis
    • Fig. 4.18b, p. 65
      Mitochondrion
      Chloroplast Specializes in photosynthesis
      Plant Cell
    • Chloroplast Structure
    • Fig. 4.18c, p. 65
      thylakoids (inner membrane system folded into flattened disks)
      two outer membranes
      stroma
    • Other Plastids
    • Chromoplasts are plastids that make and store pigments other than chlorophylls
      • Red, orange, and yellow pigments color many flowers, leaves, fruits, and roots
    • Amyloplasts store starch grains
      • Abundant in starch-storing cells of stems, tubers (underground stems), and seeds
    • 4.10 The Dynamic Cytoskeleton
    • A cytoskeleton includes microtubules , microfilaments , and intermediate filaments
    • cytoskeleton
      • Dynamic framework of protein filaments that support, organize, and move eukaryotic cells and their internal structures
    • Key Terms
    • microtubule
      • Cytoskeletal element involved in cellular movement; hollow filament of tubulin subunits
    • microfilament
      • Reinforcing cytoskeletal element; a fiber of actin subunits
    • intermediate filament
      • Cytoskeletal element that locks cells and tissues together
    • Microtubules
    • Microtubules assemble, separate the cell’s duplicated chromosomes, then disassemble
    • Examples of Microtubules
    • Microtubules (yellow) support and guide the growing ends of young nerve cells
    • Examples of Microfilaments
    • Myosin and actin microfilaments interact in contraction of muscle cells
    • cell cortex
      • Reinforcing mesh of microfilaments under a plasma membrane
    • Examples of Intermediate Filaments
    • The nuclear envelope is supported by an inner layer of intermediate filaments called lamins
    • Intermediate filaments connect to structures that lock cell membranes together in tissues
    • Fig. 4.19b, p. 66
      Microfilament
      Microtubule
      Intermediate filament
      one polypeptide chain
      actin subunit
      tubulin subunit
    • Animation: Cytoskeletal Components
    • Accessory Molecules
    • Motor proteins move cell parts when energized by a phosphate-group transfer from ATP
    • motor protein
      • Energy-using protein that interacts with cytoskeletal elements to move the cell’s parts or the whole cell
    • Motor Proteins
    • Kinesin ( tan) drags a pink vesicle along a microtubule
    • Animation: Motor Proteins
    • Motor Proteins
    • Dynein interacts with arrays of microtubules to bring about movement of eukaryotic flagella and cilia
    • Flagella and Cilia
    • A 9+2 array of microtubules extends lengthwise through a flagellum or cilium
    • The microtubules grow from a barrel-shaped centriole , which remains below the finished array as a basal body
    • Key Terms
    • cilium
      • Short, movable structure that projects from the plasma membrane of some eukaryotic cells
    • centriole
      • Barrel-shaped organelle from which microtubules grow
    • basal body
      • Organelle that develops from a centriole
    • Flagella and Cilia
    • 9+2 array: a ring of nine pairs of microtubules plus one pair at its core
    • Fig. 4.22a, p. 67
      pair of microtubules in a central sheath
      pair of microtubules
      dynein arms
      plasma membrane
      protein spokes
      A Sketch and micrograph of one eukaryotic flagellum, cross-section. Like a cilium, it contains a 9+2 array: a ring of nine pairs of microtubules plus one pair at its core. Stabilizing spokes and linking elements that connect to the microtubules keep them aligned in this radial pattern.
    • Fig. 4.22b, p. 67
      B Projecting from each pair of microtubules in the outer ring are “arms” of dynein, a motor protein that has ATPase activity. Phosphate-group
      transfers from ATP cause the dynein arms to repeatedly bind the adjacent pair of microtubules, bend, and then disengage. The dynein arms “walk” along the microtubules. Their motion causes adjacent microtubule pairs to slide past one another
      C Short, sliding strokes occur in a coordinated sequence around the ring, down the length of each microtubule
      pair. The flagellum bends as the array inside bends:
      basal body, a microtubule organizing center that gives rise to the 9+2 array and then remains beneath it, inside the cytoplasm
      Flagella and Cilia
    • Animation: Flagella Structure
    • False Feet
    • Pseudopods move the cell and engulf prey
    • Motor proteins attached to microfilaments drag the plasma membrane
    • 4.11 Cell Surface Specializations
    • Most cells of multicelled organisms are surrounded by a complex mixture of fibrous proteins and polysaccharides called extracellular matrix, or ECM
    • extracellular matrix (ECM)
      • Complex mixture of cell secretions
      • Supports cells and tissues
      • Has roles in cell signaling
    • ECM: Cuticle
    • cuticle
      • Secreted covering at a body surface
      • Chitin covering protects arthropods
      • Waxy coat protects plant’s exposed surfaces
    • Fig. 4.23, p. 68
      photosynthetic cell inside leaf
      thick, waxy cuticle at leaf surface
      cell of leaf epidermis
    • Animal ECM
    • ECM in animals consists of various carbohydrates and proteins; it is the basis of tissue organization, and provides structural support
    • Example: Bone is mostly extracellular matrix composed of collagen, a fibrous protein, hardened by mineral deposits
    • Plant ECM
    • Plant cell wall is a type of ECM: Pliable primary walls enclose secondary walls strengthened with lignin
    • primary wall
      • The first cell wall of young plant cells
    • secondary wall
      • Lignin-reinforced wall inside the primary wall of a plant cell
    • lignin
      • Material that stiffens cell walls of vascular plants
    • Fig. 4.24a, p. 68
      A Plant cell secretions form the middle lamella, a layer that cements adjoining cells together.
      B In many plant tissues, cells also secrete materials that are deposited in layers on the inner surface of their primary wall. These layers strengthen the wall and maintain its shape. They remain after the cells die, and become part of pipelines that carry water through the plant.
      primary cell wall
      cytoplasm
      pipeline made of abutting cell walls
      primary cell wall
      secondary cell wall (added in layers)
      middle lamella
      plasma membrane
      Plant Cell Walls
    • Animation: Plant Cell Walls
    • Plant Cell Junctions
    • In plants, open channels called plasmodesmata (plasmodesma) extend across cell walls, connecting the cytoplasm of adjoining cells
    • plasmodesmata
      • Cell junctions that connect the cytoplasm of adjacent plant cells
      • Allow water, nutrients, and signaling molecules to flow quickly from cell to cell
    • Fig. 4.24c, p. 68
      middle lamella
      C Plasmodesmata are channels across the cell walls and the plasma membranes of living cells that are pressed against one another in tissues.
      middle lamella
      plasmodesma
      Plasmodesmata
    • Cell Junctions in Animals
    • In animal tissues, cells are connected to their neighbors and to ECM by cell junctions
    • cell junction
      • Structure that connects a cell to another cell or to extracellular matrix
      • Cells send and receive ions, molecules, or signals through some junctions
      • Other kinds help cells recognize and stick to each other and to extracellular matrix
    • Types of Cell Junctions
    • tight junctions
      • Arrays of fibrous proteins; join epithelial cells and collectively prevent fluids from leaking between them
    • adhering junction
      • Cell junction that anchors cells to each other or to extracellular matrix
    • gap junction
      • Cell junction that forms a channel across the plasma membranes of adjoining animal cells
    • Fig. 4.25, p. 69
      adhering junction
      gap junction
      tight junctions
      free surface of epithelial tissue
      basement membrane (extracellular matrix)
      Types of Cell Junctions
    • Animation: Animal Cell Junctions
    • 4.12 Summary: Plant Cells
    • 4.12 Summary: Plant Cells
    • Fig. 4.26a, p. 70
      Energy powerhouse; produces many ATP by aerobic respiration
      Lysosome-like Vesicle Digests, recycles materials
      Golgi Body Finishes, sorts, ships lipids, enzymes, and proteins
      Smooth ER Makes lipids, breaks down carbohydrates and fats, inactivates toxins
      Rough ER Modifies proteins made by ribosomes attached to it
      Ribosomes (attached to rough ER and free in cytoplasm) Sites of protein synthesis
      Nucleus Keeps DNA separated from cytoplasm; makes ribosome subunits; controls access to DNA
      nuclear envelope
      Central Vacuole Increases cell surface area; stores metabolic wastes
      A Typical plant cell components
      Cell Wall Protects, structurally supports cell
      Chloroplast Specializes in photosynthesis
      Plasma Membrane Selectively controls the kinds and amounts of substances moving into and out of cell; helps maintain cytoplasmic volume, composition
      microtubules
      microfilaments
      intermediate filaments (not shown)
      Plasmodesma Communication junction between adjoining cells
      Cytoskeleton Structurally supports, imparts shape to cell; moves cell and its components
      Mitochondrion
      DNA in nucleoplasm
      nucleolus
    • Animation: Common Eukaryotic Organelles
    • Summary: Animal Cells
    • Fig. 4.26b, p. 70
      B Typical animal cell components.
      Plasma Membrane Selectively controls the kinds and amounts of substances moving into and out of cell; helps maintain cytoplasmic volume, composition
      microtubules
      Cytoskeleton Structurally supports, imparts shape to cell; moves cell and its components
      Energy powerhouse; produces many ATP by aerobic respiration
      Mitochondrion
      Special centers that produce and organize microtubules
      Centrioles
      Golgi Body Finishes, sorts, ships lipids, enzymes, and proteins
      Smooth ER Makes lipids, breaks down carbohydrates and fats, inactivates toxins
      Rough ER Modifies proteins made by ribosomes attached to it
      Ribosomes (attached to rough ER and free in cytoplasm) Sites of protein synthesis
      Lysosome Digests, recycles materials
      Nucleus Keeps DNA separated from cytoplasm; makes ribosome subunits; controls access to DNA
      nuclear envelope
      DNA in nucleoplasm
      nucleolus
      Intermediate filaments
      microfilaments
    • Summary: Cell Components
    • Key Concepts
    • Eukaryotic Cells
      • Cells of protists, plants, fungi, and animals are eukaryotic
      • They have a nucleus and other membrane-enclosed compartments
      • Cells differ in internal parts and surface specializations
    • 4.13 The Nature of Life
    • Life is a property that emerges from cellular components, but a collection of those components in the right amounts and proportions is not necessarily alive
    • Characteristics of life:
      • A set of properties unique to living things
      • Collectively, these properties characterize living things as different from nonliving things
    • Characteristics of Living Things
    • They make and use organic molecules of life
    • They consist of one or more cells
    • They engage in self-sustaining biological processes such as metabolism and homeostasis
    • They change over their lifetime by growing, maturing, and aging
    • They use DNA as hereditary material
    • They have the collective capacity to change over successive generations by adapting to environmental pressures
    • Food for Thought (revisited)
    • Meat, poultry, milk, and fruits sterilized by exposure to radiation are available in supermarkets
    • By law, irradiated foods must be marked with a special symbol:
    • Foods sterilized with chemicals are not currently required to carry any disclosure