Biology of the Cell: Cell Structure Guide PDF

Faculty of Education BESPFT Natural Sciences 1 (Life Sciences) NSC152S Topic 2 BIOLOGY OF THE CELL An introduction to cell structure 1 Cell Theory States that: All organisms are composed o...

Faculty of Education BESPFT Natural Sciences 1 (Life Sciences) NSC152S Topic 2 BIOLOGY OF THE CELL An introduction to cell structure 1 Cell Theory States that: All organisms are composed of cells German botanist Matthias Schleiden in 1838 German zoologist Theodor Schwann in 1839 All cells come only from preexisting cells German physician Rudolph Virchow in 1850’s Cells are the smallest structural and functional unit of organisms 2 Organisms and Cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. c. b. 50 m d. 140 m a: © Geoff Bryant/Photo Researchers, Inc.; b: Courtesy Ray F. Evert/University of Wisconsin Madison; c: © Barbara J. Miller/Biological Photo Service; d: Courtesy O. Sabatakou and E. Xylouri-Frangiadak 4 Cell Size Cells are very small Cells range in size from one millimeter down to one micrometer /micron – symbol is µm Cells need a large surface area of plasma membrane to adequately exchange materials. The surface‑area‑to‑volume ratio requires that cells be small Large cells - surface area relative to volume decreases Volume is living cytoplasm, which demands nutrients and produces wastes Cells specialized in absorption utilize membrane modifications such as microvilli to greatly increase surface area per unit volume 5 Sizes of Living Things Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 0.1 nm 1 nm 10 nm 100 nm 1 m 10 m 100 m 1 mm 1 cm 0.1 m 1m 10 m 100 m 1 km protein chloroplast plant and mouse rose animal frog egg amino cells acid virus ostrich most bacteria human egg ant egg atom blue whale electron microscope human light microscope human eye 6 The sizes of cells and their contents (Vodopich and Moore, 2011, Biology laboratory manual, 9th Ed.) Types of microscopes Can only be studied when magnified/enlarged through the lenses of microscopes and by making use of various staining methods The development and refinement of different types of microscopes allow for cells, their structure and properties to be explored. E.g. compound light microscope, transmission electron microscope, scanning electron microscope, confocal microscope Compound Light Microscope (used in lab) Light passed through specimen Focused by glass lenses Image formed on human retina Max magnification about 1000X Resolves objects separated by 0.2 mm, 500X better than human eye Scanning electron microscope Abbreviated S.E.M. Specimen sprayed with thin coat of metal Electron beam scanned across surface of specimen Metal emits secondary electrons Emitted electrons focused by magnetic lenses Image formed on fluorescent screen Similar to TV screen Image is then photographed Confocal microscope Narrow laser beam scanned across transparent specimen Beam is focused at a very thin plane Allows microscopist to optically section a specimen Sections made at different levels Allows assembly of 3d image on computer screen that can be rotated Amoeba proteus under different types of microscopes Cellular organization Structural similarities of all cells: A plasma membrane that encloses the cell Filled with a semi-fluid matrix called the cytoplasm Organelles are suspended in the cytoplasm Cytosol is the cytoplasm without the organelles Genetic material (DNA) is found inside the cell TWO main cell types: prokaryotic and eukaryotic Based on organization of the DNA, cells are classified as prokaryotic or eukaryotic Prokaryotic cells – single DNA molecule, near centre of cell, in area called the nucleoid and not bounded by a membrane Eukaryotic – DNA contained in a nucleus, surrounded by a double nuclear membrane Prokaryotic cells are placed in two taxonomic domains: Bacteria Archaea Domain Eukarya includes: Protists Fungi Plants Animals The Structure of Bacteria – a prokaryote Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Ribosome: Fimbriae: site of protein synthesis hairlike bristles that allow adhesion to the surfaces Inclusion body: Conjugation pilus: stored nutrients elongated, hollow for appendage used for later use Mesosome: DNA transfer to other plasma membrane bacterial cells that folds into the Nucleoid: cytoplasm and location of the bacterial increases surface area chromosome Plasma membrane: sheath around cytoplasm that regulates entrance and exit of molecules Cell wall: covering that supports, shapes, and protects cell Glycocalyx: gel-like coating outside cell wall; if compact, called a capsule; if diffuse, called a slime layer Flagellum: rotating filament present Escherichia coli in some bacteria that pushes the cell forward © Howard Sochurek/The Medical File/Peter Arnold, Inc. 15 Differences between prokaryotes and eukaryotes General structure of eukaryotic cells are more complex than prokaryotic cells possess a membrane-bound nucleus DNA wound around proteins called histones compartmentalize many cellular functions within organelles and the endomembrane system possess a cytoskeleton for support and to maintain cellular structure Histones Animal Cell Anatomy Copyright © The McGraw-Hill Companies, Inc. 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Plasma membrane: outer surface that regulates entrance and exit of molecules protein phospholipid Nucleus: command center of cell Nuclear envelope: double Cytoskeleton: maintains membrane with nuclear pores cell shape and assists movement that encloses nucleus of cell parts: Chromatin: diffuse threads containing DNA and protein Microtubules: protein Nucleolus: region that produces cylinders that move subunits of ribosomes organelles Endoplasmic reticulum: Intermediate filaments: protein and lipid metabolism protein fibers that provide Rough ER: studded with stability of shape ribosomes that synthesize Actin filaments: protein proteins fibers that play a role in Smooth ER: lacks change of shape ribosomes, synthesizes lipid molecules Centrioles*: short Peroxisome: vesicle cylinders of microtubules that is involved in of unknown function fatty acid metabolism Centrosome: microtubule Ribosomes: organizing center that particles that carry contains a pair of centrioles out protein synthesis Lysosome*: vesicle that Polyribosome: string of digests macromolecules ribosomes simultaneously and even cell parts synthesizing same protein Vesicle: small membrane- bounded sac that stores and transports substances Mitochondrion: organelle Cytoplasm: semifluid that carries out cellular respiration, matrix outside nucleus producing ATP molecules that contains organelles Golgi apparatus: processes, packages, *not in plant cells and secretes modified proteins 19 Plant Cell Anatomy Copyright © The McGraw-Hill Companies, Inc. 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Nucleus: command center of cell Central vacuole*: large, fluid-filled Nuclear envelope: double membrane with sac that stores metabolites and nuclear pores that encloses nucleus helps maintain turgor pressure Nucleolus: produces subunits of ribosomes Chromatin: diffuse threads containing Cell wall of adjacent cell DNA and protein Nuclear pore: permits passage of Middle lamella: proteins into nucleus and ribosomal cements together the subunits out of nucleus primary cell walls of Ribosomes: carry adjacent plant cells out protein synthesis Chloroplast*: carries Centrosome: out photosynthesis, microtubule organizing producing sugars center (lacks centrioles) Granum*: a stack Endoplasmic of chlorophyll-containing reticulum: protein thylakoids and lipid metabolism in a chloroplast Rough ER: studded Mitochondrion: organelle with ribosomes that that carries out cellular synthesize proteins respiration, producing ATP molecules Smooth ER: lacks ribosomes, synthesizes Microtubules: protein cylinders lipid molecules that aid movement of organelles Peroxisome: vesicle that Actin filaments: protein fibers is involved in fatty acid that play a role in movement of metabolism cell and organelles Golgi apparatus: processes, Plasma membrane: surrounds packages, and secretes cytoplasm, and regulates entrance modified proteins and exit of molecules Cytoplasm: semifluid matrix outside Cell wall*: outer surface that shapes, nucleus that contains organelles supports, and protects cell *not in animal cells 20 Activity Use the diagrams of the structure of the animal – and plant cell and make a list of all the similarities and a table of all the differences. Organelles: Nucleus Contains genetic information – DNA organized into chromatin Is membrane-bounded Nuclear envelope - consists of 2 phospholipid bilayers; outer layer continuous with the ER Nuclear lamins – on inside of nuclear envelope; maintains the shape of the nucleus Nuclear pores – allow for exchange of small molecules between the nucleoplasm and the cytoplasm Nucleolus – region of nucleoplasm where the rRNA is transcribed and ribosomes are assembled Eukaryotic Cells 23 Organelles: ribosomes Consists of 2 subunits that are composed of ribosomal RNA and protein Can be free in the cytosol or bound to the ER Use information in mRNA to direct the synthesis of proteins Nucleus, Ribosomes, & ER Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cytoplasm Endoplasmic reticulum (ER) ER membrane protein 4. An enzyme removes the signal peptide. Lumen of ER 5. Ribosomal subunits and mRNA break away. The protein remains in the ER enzyme and folds into its final shape. mRNA receptor SRP signal recognition particle (SRP) 2. Signal recognition 3. SRP attaches to receptor (purple); particle (SRP) binds a channel opens; and the to signal peptide. polypeptide enters ER.. signal peptide ribosomal subunits nuclear pore ribosome mRNA mRNA DNA 1. mRNA is leaving the nucleus and is attached Nucleus to the ribosome; protein synthesis is occurring. 25 Organelles: endomembrane system a series of membranes throughout the cytoplasm divides cell into compartments where different cellular functions occur provides channels to carry molecules to surfaces for the synthesis of macromolecules 1. endoplasmic reticulum 2. Golgi apparatus 3. lysosomes 4. vacuoles 5. microbodies Endomembrane System 27  Endomembrane System: The Endoplasmic Reticulum A system of membrane channels and saccules (flattened vesicles) continuous with the outer membrane of the nuclear envelope Rough ER Studded with ribosomes on cytoplasmic side Protein anabolism Synthesizes proteins Modifies and processes proteins Adds sugar to protein Results in glycoproteins Smooth ER No ribosomes Synthesis of lipids Site of various synthetic processes, detoxification, and storage Forms transport vesicles 28 Endoplasmic Reticulum Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ribosomes nuclear envelope rough endoplasmic reticulum smooth endoplasmic reticulum 0.08 m © R. Bolender & D. Fawcett/Visuals Unlimited 29  Endomembrane System: The Golgi Apparatus Consists of 3-20 flattened, membranous sacs All the Golgi bodies collectively referred to as the Golgi apparatus Has polarity – cis and trans faces Involved in the synthesis of many polysaccharides Modifies proteins and lipids Receives vesicles from ER on cis (or inner face) Packages them in vesicles Prepares for “shipment” in vesicles Packages them in vesicles from trans (or outer face) Within cell Export from cell (secretion, exocytosis) 30 Golgi Apparatus Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. secretion transport saccules vesicle transport vesicle trans face cis face Golgi apparatus Nucleus 0.1 m Courtesy Charles Flickinger, from Journal of Cell Biology 49: 221-226, 1971, Fig. 1 page 224 31  Endomembrane System: Lysosomes Membrane-bound small, spherical vesicles (not in plant cells) Produced by the Golgi apparatus or ER Contain powerful digestive/hydrolytic enzymes and are highly acidic Digestion of large molecules Recycling of cellular resources by means of autolysis (dead cell digested by enzymes of its own lysosomes) Apoptosis (programmed cell death, like tadpole losing tail) Some genetic diseases Caused by defect in lysosomal enzyme Lysosomal storage diseases (Tay-Sachs) 32 Lysosomes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. lysosome mitochondrion peroxisome fragment a. Mitochondrion and a peroxisome in a lysosome b. Storage bodies in a cell with defective lysosomes a: Courtesy Daniel S. Friend; b: Courtesy Robert D. Terry/Univ. of San Diego School of Medicine 33 Relationships among organelles of the endomembrane system Animation Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. 35 Endomembrane system: microbodies: peroxisomes Found in all eukaryotic cells (animal cells, plant cells, fungi and protists) Similar to lysosomes Membrane-bounded vesicles Enclose enzymes However Enzymes synthesized by free ribosomes in cytoplasm (instead of ER) Active in lipid metabolism Catalyze reactions that produce hydrogen peroxide H2O2 Toxic Broken down to water & O2 by catalase Endomembrane system: Peroxisomes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 100 nm © S.E. Frederick & E.H. Newcomb/Biological Photo Service 37 Endomembrane system: microbodies: glyoxysomes Found in plant cells only Contain enzymes that convert fats into carbohydrates Endomembrane system: Vacuoles Membranous sacs that are larger than vesicles Store materials that occur in excess Others very specialized (contractile vacuole) Plants cells typically have a central vacuole Up to 90% volume of some cells Functions in: Storage of water, nutrients, pigments, and waste products Development of turgor pressure Some functions performed by lysosomes in other eukaryotes 39 Endomembrane system: Vacuoles Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 100 nm © Newcomb/Wergin/Biological Photo Service 40 Organelles: Plastids Chloroplasts, chromoplasts and leucoplasts are collectively known as plastids All plastids are produced by the division of existing plastids Leucoplasts can change into chloroplasts and vice versa Chloroplasts that changed into chromoplasts gives fruit, vegetables and flowers their bright colours  Energy-Related Organelles: Chloroplasts Membranous organelles (a type of plastid) that serve as the site of photosynthesis - captures light energy to produce ATP and sugars Larger and more complex than mitochondria Surrounded by a double membrane Closed compartments of stacked membranes called grana ( 100 or more) Each granum contains a few to several dozen disc-shaped structures called thylakoids On the surface of the thylakoids are the light-capturing photosynthetic pigments such as chlorophyll which gives plants their green colour The thylakoids are surrounded by a fluid matrix called the stroma42  Photosynthesis Synthesizes carbohydrates from CO2 & H2O Makes own food using CO2 as only carbon source Energy-poor compounds converted to energy-rich compounds solar energy + carbon dioxide + water → carbohydrate + oxygen Only plants, algae, and certain bacteria are capable of conducting photosynthesis Chloroplast Structure Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. 500 nm outer thylakoid membrane grana space stroma thylakoid membrane double inner membrane membrane b. a: Courtesy Herbert W. Israel, Cornell University 44  EOrganellesnergy-Oelated Organelles: Mitochondria Energy-related organelles: mitochondria Smaller than chloroplast – about the size of bacteria Contain ribosomes and their own DNA Surrounded by a double membrane Inner membrane surrounds the matrix and is convoluted (folds) to form cristae. Matrix – Inner semi-fluid containing respiratory enzymes Break down carbohydrates Involved in cellular respiration Produce most of ATP utilized by the cell 45 Mitochondrial Structure Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. 200 nm outer membrane cristae matrix double inner membrane membrane b. a: Courtesy Dr. Keith Porter 46 Mitochondria and chloroplasts share structural similarities such as: Both are surrounded by a double membrane Both contain their own DNA Both have the apparatus for protein synthesis Both are involved in energy metabolism Both have evolved from prokaryotes – according to the endosymbiont theory (mitochondria have evolved from bacteria capable of oxidative metabolism and chloroplasts have evolved from photosynthetic bacteria) Endosymbiont theory: Mitochondria & Chloroplasts 48  The cytoskeleton Cyceetoskeleton Maintains cell shape Assists in movement of cell and organelles Three types of macromolecular fibers Actin Filaments Intermediate Filaments Microtubules Assemble and disassemble as needed 49 The Cytoskeleton Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. actin subunit Chara a. Actin filaments fibrous subunits peacock b. Intermediate filaments tubulin dimer chameleon c. Microtubules a(Actin): © M. Schliwa/Visuals Unlimited; b, c(Intermediate, Microtubules): © K.G. Murti/Visuals Unlimited; a(Chara): The McGraw-Hill Companies, Inc./photo by Dennis Strete and Darrell Vodopich; b(Peacock): © Vol. 86/Corbis; c(Chameleon): © Photodisc/Vol. 6/Getty Images 50 The Cytoskeleton: Actin Filaments Extremely thin filaments like twisted pearl necklace 7 nm in diameter Dense web just under plasma membrane maintains cell shape Support for microvilli in intestinal cells Intracellular traffic control For moving stuff around within cell Cytoplasmic streaming Function in pseudopods of amoeboid cells Pinch mother cell in two after animal mitosis Important component in muscle contraction (other is myosin) 51 The Cytoskeleton: Actin Filament Operation Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. actin filament ATP ADP + P myosin molecules tail head membrane 52  The Cytoskeleton: Intermediate Filaments Intermediate in size between actin filaments and microtubules About 8 to 10nm in diameter Rope-like assembly of fibrous polypeptides Stable and do not break down Functions: Support nuclear envelope Cell-cell junctions, like those holding skin cells tightly together 53 The Cytoskeleton: Microtubules Hollow cylinders made of two globular proteins called a and b tubulin About 25nm in diameter Largest of the protein fibres in the cytoskeleton Under control of Microtubule Organizing Center (MTOC) Most important MTOC is centrosome Interacts with proteins kinesin and dynein to:  cause movement of organelles  movement of cells  provide organization to the cytoplasm and are responsible for moving materials inside the cell itself by means of molecular motors 54 The Cytoskeleton: Microtubule Operation Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ATP vesicle kinesin kinesin receptor vesicle moves, not microtubule 55 Cytoskeleton: Centrioles Short, hollow cylinders Composed of 27 microtubules Microtubules arranged into 9 overlapping triplets One pair per animal cell Located in centrosome of animal cells Oriented at right angles to each other Separate during mitosis to determine plane of division May give rise to basal bodies of cilia and flagella 56 Cytoskeleton: Centrioles Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. empty center of centriole one microtubule triplet one centrosome: one pair of centrioles two centrosomes: two pairs of centrioles 200 nm (Middle): Courtesy Kent McDonald, University of Colorado Boulder; (Bottom): Journal of Structural Biology, Online by Manley McGill et al. Copyright 1976 by Elsevier Science & Technology Journals. Reproduced with permission of Elsevier Science & Technology Journals in the format Textbook via Copyright Clearance 57 Center  Extracellular structures: Cilia and Flagella Hair-like projections from cell surface that aid in cell movement Very different from prokaryote flagella Outer covering of plasma membrane Inside this is a cylinder of 18 microtubules arranged in 9 pairs In center are two single microtubules This 9 + 2 pattern used by all cilia & flagella In eukaryotes, cilia are much shorter than flagella Cilia move in coordinated waves like oars Flagella move like a propeller or cork screw 58 Structure of a Flagellum Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. outer Flagellum microtubule doublet radial spoke central shaft The shaft of the microtubules flagellum has a ring of nine microtubule doublets anchored dynein to a central pair of side arm microtubules. 25 nm Flagellum cross section The side arms dynein Sperm of each doublet side arms plasma are composed triplets membrane of dynein, a motor molecule. Basal body ATP In the presence of ATP, the dynein side arms reach out to their neighbors, The basal body of a flagellum has and bending occurs. 100 nm a ring of nine microtubule triplets Basal body cross section with no central microtubules. (Flagellum, Basal body): © William L. Dentler/Biological Photo Service 59 Extracellular Structures: cell walls Include cell walls of plants, fungi, some protists And the extracellular matrix surrounding animal cells Provide protection, support, strength and cell recognition 60 Extracellular Structures: cell walls Protect and surround the cells of plants, fungi, and some protists the carbohydrates present in the cell wall vary depending on the cell type: -plant and protist cell walls - cellulose -fungal cell walls – chitin In plant cells, while the cell is still growing the primary wall is laid down Between the walls of adjacent cells, a sticky substance called pectin forms the middle lamella that glues cells together In some plant cells a strong secondary wall of lignin is laid down inside the primary walls of fully expanded cells 61 Extracellular Structures Extracellular matrix (ECM) -surrounds animal cells- animal cells lack cell walls -composed of glycoproteins and fibrous proteins such as collagen -may be connected to the cytoplasm via integrin proteins present in the plasma membrane 63 Extracellular Structures 64 65 66