Transcript Chapter 13
Chapter 3 Cell Structure and Function © 2012 Pearson Education Inc. Lecture prepared by Mindy Miller-Kittrell North Carolina State University Processes of Life • • • • Growth Reproduction Responsiveness Metabolism © 2012 Pearson Education Inc. Figure 3.1 Examples of types of cells-overview Prokaryotic and Eukaryotic Cells: An Overview • Prokaryotes – Lack nucleus – Lack various internal structures bound with phospholipid membranes – Are small (~1.0 µm in diameter) – Have a simple structure – Include bacteria and archaea © 2012 Pearson Education Inc. Figure 3.2 Typical prokaryotic cell Inclusions Ribosome Cytoplasm Flagellum Nucleoid Glycocalyx Cell wall Cytoplasmic membrane Prokaryotic and Eukaryotic Cells: An Overview • Eukaryotes – – – – – Have nucleus Have internal membrane-bound organelles Are larger (10–100 µm in diameter) Have more complex structure Include algae, protozoa, fungi, animals, and plants © 2012 Pearson Education Inc. Figure 3.3 Typical eukaryotic cell Nuclear envelope Nuclear pore Nucleolus Lysosome Mitochondrion Centriole Secretory vesicle Golgi body Cilium Transport vesicles Ribosomes Rough endoplasmic reticulum Smooth endoplasmic reticulum Cytoplasmic membrane Cytoskeleton Figure 3.4 Approximate size of various types of cells Virus Orthopoxvirus 0.3 m diameter Bacterium Staphylococcus 1 m diameter Chicken egg 4.7 cm diameter (47,000 m)* Parasitic protozoan Giardia 14 m length *Actually, the inset box on the egg would be too small to be visible. (Width of box would be about 0.002 mm.) External Structures of Bacterial Cells • Glycocalyces – Gelatinous, sticky substance surrounding the outside of the cell – Composed of polysaccharides, polypeptides, or both © 2012 Pearson Education Inc. External Structures of Bacterial Cells • Two Types of Glycocalyces – Capsule – Composed of organized repeating units of organic chemicals – Firmly attached to cell surface – May prevent bacteria from being recognized by host – Slime layer – Loosely attached to cell surface – Water soluble – Sticky layer allows prokaryotes to attach to surfaces © 2012 Pearson Education Inc. Figure 3.5 Glycocalyces-overview Glycocalyx (capsule) Glycocalyx (slime layer) External Structures of Bacterial Cells ANIMATION Motility © 2012 Pearson Education Inc. External Structures of Bacterial Cells • Flagella – Are responsible for movement – Have long structures that extend beyond cell surface – Are not present on all bacteria © 2012 Pearson Education Inc. External Structures of Bacterial Cells • Flagella – Structure – Composed of filament, hook, and basal body – Basal body anchors filament and hook to cell wall by a rod and a series of either two or four rings of integral proteins © 2012 Pearson Education Inc. External Structures of Bacterial Cells ANIMATION Flagella: Structure © 2012 Pearson Education Inc. Figure 3.6 Proximal structure of bacterial flagella-overview Filament Direction of rotation during run Rod Peptidoglycan layer (cell wall) Protein rings Cytoplasmic membrane Cytoplasm Filament Gram Outer protein rings Rod Gram Basal body Outer membrane Peptidoglycan layer Integral protein Inner protein rings Integral protein Cytoplasm Cytoplasmic membrane Cell wall Figure 3.7 Micrographs of basic arrangements of bacterial flagella-overview External Structures of Bacterial Cells ANIMATION Flagella: Arrangement ANIMATION Flagella: Spirochetes © 2012 Pearson Education Inc. Figure 3.8 Axial filament-overview Endoflagella rotate Axial filament Axial filament rotates around cell Outer membrane Cytoplasmic membrane Spirochete corkscrews and moves forward Axial filament External Structures of Bacterial Cells • Flagella – Function – Rotation propels bacterium through environment – Rotation reversible; can be counterclockwise or clockwise – Bacteria move in response to stimuli (taxis) – Runs – Tumbles © 2012 Pearson Education Inc. Figure 3.9 Motion of a peritrichous bacterium Attractant Run Tumble Run Tumble External Structures of Bacterial Cells ANIMATION Flagella: Movement © 2012 Pearson Education Inc. External Structures of Bacterial Cells • Fimbriae and Pili – Rodlike proteinaceous extensions © 2012 Pearson Education Inc. External Structures of Bacterial Cells • Fimbriae – Sticky, bristlelike projections – Used by bacteria to adhere to one another, to hosts, and to substances in environment – Shorter than flagella – Serve an important function in biofilms © 2012 Pearson Education Inc. Figure 3.10 Fimbriae Flagellum Fimbria External Structures of Bacterial Cells • Pili – Special type of fimbria – Also known as conjugation pili – Longer than other fimbriae but shorter than flagella – Bacteria typically have only one or two per cell – Mediate the transfer of DNA from one cell to another (conjugation) © 2012 Pearson Education Inc. Figure 3.11 Pili Conjugation pilus Bacterial Cell Walls • Bacterial Cell Walls – Provide structure and shape and protect cell from osmotic forces – Assist some cells in attaching to other cells or in resisting antimicrobial drugs – Can target cell wall of bacteria with antibiotics – Give bacterial cells characteristic shapes – Composed of peptidoglycan – Scientists describe two basic types of bacterial cell walls, Gram-positive and Gram-negative © 2012 Pearson Education Inc. Figure 3.12 Bacterial shapes and arrangements-overview Figure 3.13 Comparison of the structures of glucose, NAG, and NAM-overview Glucose N-acetylglucosamine NAG N-acetylmuramic acid NAM Bacterial Cell Walls • Gram-Positive Bacterial Cell Walls – – – – Relatively thick layer of peptidoglycan Contain unique polyalcohols called teichoic acids Appear purple following Gram staining procedure Up to 60% mycolic acid in acid-fast bacteria helps cells survive desiccation © 2012 Pearson Education Inc. Figure 3.15a Comparison of cell walls of Gram-positive and Gram-negative bacteria Peptidoglycan layer (cell wall) Cytoplasmic membrane Gram-positive cell wall Lipoteichoic acid Teichoic acid Integral protein Bacterial Cell Walls • Gram-Negative Bacterial Cell Walls – Have only a thin layer of peptidoglycan – Bilayer membrane outside the peptidoglycan contains phospholipids, proteins, and lipopolysaccharide (LPS) – May be impediment to the treatment of disease – Appear pink following Gram staining procedure © 2012 Pearson Education Inc. Figure 3.15b Comparison of cell walls of Gram-positive and Gram-negative bacteria Porin Outer membrane of cell wall Porin (sectioned) Peptidoglycan layer of cell wall Gram-negative cell wall n Cytoplasmic membrane Phospholipid layers Lipopolysaccharide (LPS) O side chain (varies In length and composition) Integral proteins Core polysaccharide Lipid A (embedded in outer membrane) Periplasmic space Fatty acid Bacterial Cytoplasmic Membranes • Structure – Referred to as phospholipid bilayer – Composed of lipids and associated proteins – Fluid mosaic model describes current understanding of membrane structure © 2012 Pearson Education Inc. Figure 3.16 The structure of a prokaryotic cytoplasmic membrane: a phospholipid bilayer Head, which contains phosphate (hydrophilic) Phospholipid Tail (hydrophobic) Integral proteins Cytoplasm Integral protein Phospholipid bilayer Peripheral protein Integral protein Bacterial Cytoplasmic Membranes • Function – – – – – – Energy storage Harvest light energy in photosynthetic bacteria Selectively permeable Naturally impermeable to most substances Proteins allow substances to cross membrane Maintain concentration and electrical gradient © 2012 Pearson Education Inc. Figure 3.17 Electrical potential of a cytoplasmic membrane Cell exterior (extracellular fluid) Cytoplasmic membrane Integral protein Protein DNA Protein Cell interior (cytoplasm) Bacterial Cytoplasmic Membranes • Function – Passive processes – Diffusion – Facilitated diffusion – Osmosis © 2012 Pearson Education Inc. Figure 3.18 Passive processes of movement across a cytoplasmic membrane-overview Extracellular fluid Cytoplasm Diffusion through the phospholipid bilayer Facilitated diffusion through a nonspecific channel protein Facilitated diffusion Osmosis, through a permease specific for one chemical; binding of substrate causes shape change in the channel protein the diffusion of water through a specific channel protein or through the phospholipid bilayer Figure 3.19 Osmosis, the diffusion of water across a selectively permeable membrane-overview Solutes Semipermeable membrane allows movement of H2O, but not of solutes Figure 3.20 Effects of isotonic, hypertonic, and hypotonic solutions on cells-overview Cells without a wall (e.g., mycoplasmas, animal cells) H2O H2O H2O Cell wall Cells with a wall (e.g., plants, fungal and bacterial cells) Cell wall H2O H2O Cell membrane Isotonic solution H2O Cell membrane Hypertonic solution Hypotonic solution Bacterial Cytoplasmic Membranes • Function – Active processes – Active transport – Group translocation – Substance chemically modified during transport © 2012 Pearson Education Inc. Figure 3.21 Mechanisms of active transport-overview Extracellular fluid Uniport Cytoplasmic membrane Symport Cytoplasm Uniport Antiport Coupled transport: uniport and symport Bacterial Cytoplasmic Membranes ANIMATION Active Transport: Overview ANIMATION Active Transport: Types © 2012 Pearson Education Inc. Figure 3.22 Group translocation Glucose Extracellular fluid Cytoplasm Glucose 6-PO4 Cytoplasm of Bacteria • Cytosol – Liquid portion of cytoplasm • Inclusions – May include reserve deposits of chemicals • Endospores – Unique structures produced by some bacteria that are a defensive strategy against unfavorable conditions © 2012 Pearson Education Inc. Figure 3.23 Granules of PHB in the bacterium Azotobacter chroococcum Polyhydroxybutyrate Figure 3.24 The formation of an endospore-overview Cell wall Cytoplasmic membrane DNA is replicated. DNA A cortex of calcium and dipicolinic acid is deposited between the membranes. Cortex Vegetative cell Spore coat forms around endospore. DNA aligns along the cell’s long axis. Cytoplasmic membrane invaginates to form forespore. Forespore Endospore matures: completion of spore coat and increase in resistance to heat and chemicals by unknown process. Endospore is released from original cell. Cytoplasmic membrane grows and engulfs forespore within a second membrane. Vegetative cell’s DNA disintegrates. First membrane Second membrane Spore coat Outer spore coat Endospore Outer spore coat Cytoplasm of Bacteria • Nonmembranous Organelles – Ribosomes – Sites of protein synthesis – Cytoskeleton – Plays a role in forming the cell’s basic shape © 2012 Pearson Education Inc. Figure 3.25 A simple helical cytoskeleton External Structures of Archaea • Glycocalyces – Function in the formation of biofilms – Adhere cells to one another and inanimate objects • Flagella – Consist of basal body, hook, and filament – Numerous differences with bacterial flagella • Fimbriae and Hami – Many archaea have fimbriae – Some make fimbriae-like structures called hami – Function to attach archaea to surfaces © 2012 Pearson Education Inc. Figure 3.26 Archaeal hami Hamus Grappling hook Prickles Archaeal Cell Walls and Cytoplasmic Membrane – Most archaea have cell walls – Do not have peptidoglycan – Contain variety of specialized polysaccharides and proteins – All archaea have cytoplasmic membranes – Maintain electrical and chemical gradients – Control import and export of substances from the cell © 2012 Pearson Education Inc. Figure 3.27 Representative shapes of archaea-overview Cytoplasm of Archaea – Archaeal cytoplasm similar to bacterial cytoplasm – Have 70S ribosomes – Fibrous cytoskeleton – Circular DNA – Archaeal cytoplasm also differs from bacterial cytoplasm – Different ribosomal proteins – Different metabolic enzymes to make RNA – Genetic code more similar to eukaryotes © 2012 Pearson Education Inc. External Structure of Eukaryotic Cells • Glycocalyces – – – – – Never as organized as prokaryotic capsules Help anchor animal cells to each other Strengthen cell surface Provide protection against dehydration Function in cell-to-cell recognition and communication © 2012 Pearson Education Inc. Eukaryotic Cell Walls – Fungi, algae, plants, and some protozoa have cell walls – Composed of various polysaccharides – Plant cell walls composed of cellulose – Fungal cell walls composed of cellulose, chitin, and/or glucomannan – Algal cell walls composed of a variety of polysaccharides © 2012 Pearson Education Inc. Figure 3.28 A eukaryotic cell wall Cell wall Cytoplasmic membrane Eukaryotic Cytoplasmic Membranes – – – – All eukaryotic cells have cytoplasmic membrane Are a fluid mosaic of phospholipids and proteins Contain steroid lipids to help maintain fluidity Contain regions of lipids and proteins called membrane rafts – Control movement into and out of cell © 2012 Pearson Education Inc. Figure 3.29 Eukaryotic cytoplasmic membrane Cytoplasmic membrane Intercellular matrix Cytoplasmic membrane Figure 3.30 Endocytosis-overview Pseudopodium Cytoplasm of Eukaryotes • Flagella – Structure and arrangement – Differ structurally and functionally from prokaryotic flagella – Within the cytoplasmic membrane – Shaft composed of tubulin arranged to form microtubules – Filaments anchored to cell by basal body – May be single or multiple – Function – Do not rotate but undulate rhythmically © 2012 Pearson Education Inc. Figure 3.31a Eukaryotic flagella and cilia Flagellum Figure 3.31b Eukaryotic flagella and cilia Cilia Figure 3.32 Movement of eukaryotic flagella and cilia-overview Direction of motion Flagella Direction of motion Cilia Cytoplasm of Eukaryotes • Cilia – Shorter and more numerous than flagella – Coordinated beating propels cells through their environment – Also used to move substances past the surface of the cell © 2012 Pearson Education Inc. Figure 3.31c Eukaryotic flagella and cilia Cytoplasmic membrane Cytosol Central pair microtubules Microtubules (doublet) “9 2” arrangement Cytoplasmic membrane Portion cut away to show transition area from doublets to triplets and the end of central microtubules Basal body . .. Microtubules (triplet) “9 0” arrangement Cytoplasm of Eukaryotes • Other Nonmembranous Organelles – Ribosomes – Larger than prokaryotic ribosomes (80S versus 70S) – Composed of 60S and 40S subunits – Cytoskeleton – – – – Extensive network of fibers and tubules Anchors organelles Produces basic shape of the cell Made up of tubulin microtubules, actin microfilaments, and intermediate filaments © 2012 Pearson Education Inc. Figure 3.33 Eukaryotic cytoskeleton-overview Microtubule Microfilament Actin subunit Intermediate filament Tubulin Protein subunits Cytoplasm of Eukaryotes • Other Nonmembranous Organelles – Centrioles and centrosome – Centrioles play a role in mitosis, cytokinesis, and formation of flagella and cilia – Centrosome is region of cytoplasm where centrioles are found © 2012 Pearson Education Inc. Figure 3.34 Centrosome-overview Centrosome (made up of two centrioles) Microtubules Triplet Cytoplasm of Eukaryotes • Membranous Organelles – Nucleus – Often largest organelle in cell – Contains most of the cell’s DNA – Nucleoplasm – Contains chromatin – Nucleoli present in nucleoplasm; RNA synthesized in nucleoli – Surrounded by nuclear envelope © 2012 Pearson Education Inc. Figure 3.35 Eukaryotic nucleus Nucleolus Nucleoplasm Chromatin Nuclear envelope Two phospholipid bilayers Nuclear pores Rough ER Cytoplasm of Eukaryotes • Membranous Organelles – Endoplasmic reticulum – Netlike arrangement of flattened, hollow tubules continuous with nuclear envelope – Functions as transport system – Two forms – Smooth endoplasmic reticulum (SER) – Rough endoplasmic reticulum (RER) © 2012 Pearson Education Inc. Figure 3.36 Endoplasmic reticulum Membrane-bound ribosomes Mitochondrion Free ribosome Rough endoplasmic Smooth endoplasmic reticulum (SER) reticulum (RER) Cytoplasm of Eukaryotes • Membranous Organelles – Golgi body – Flattened hollow sacs surrounded by phospholipid bilayer – Receives, processes, and packages large molecules for export from cell – Packages molecules in secretory vesicles – Not in all eukaryotic cells © 2012 Pearson Education Inc. Figure 3.37 Golgi body Secretory vesicles Vesicles arriving from ER Cytoplasm of Eukaryotes • Membranous Organelles – Lysosomes, peroxisomes, vacuoles, and vesicles – – – – Store and transfer chemicals within cells May store nutrients in cell Lysosomes contain catabolic enzymes Peroxisomes contain enzymes that degrade poisonous wastes © 2012 Pearson Education Inc. Figure 3.38 Vacuole Cell wall Nucleus Central vacuole Cytoplasm Figure 3.39 The roles of vesicles in the destruction of a phagocytized pathogen within a white blood cell Endocytosis (phagocytosis) Bacterium Phagosome (food vesicle) Vesicle fuses with a lysosome Smooth endoplasmic reticulum (SER) Transport vesicle Lysosome Phagolysosome Golgi body Secretory vesicle Exocytosis (elimination, secretion) Cytoplasm of Eukaryotes • Membranous Organelles – Mitochondria – Have two membranes composed of phospholipid bilayer – Produce most of cell’s ATP – Interior matrix contains 70S ribosomes and molecule of DNA © 2012 Pearson Education Inc. Figure 3.40 Mitochondrion Outer membrane Inner membrane Crista Matrix Ribosomes Cytoplasm of Eukaryotes • Membranous Organelles – Chloroplasts – Light-harvesting structures found in photosynthetic eukaryotes – Have two phospholipid bilayer membranes and DNA – Have 70S ribosomes © 2012 Pearson Education Inc. Figure 3.41 Chloroplast Granum Stroma Thylakoid space Thylakoid Inner bilayer membrane Outer bilayer membrane Cytoplasm of Eukaryotes • Endosymbiotic Theory – Eukaryotes formed from union of small aerobic prokaryotes with larger anaerobic prokaryotes – Smaller prokaryotes became internal parasites – Parasites lost ability to exist independently – Larger cell became dependent on parasites for aerobic ATP production – Aerobic prokaryotes evolved into mitochondria – Similar scenario for origin of chloroplasts – Not universally accepted © 2012 Pearson Education Inc.