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Transcript
How Cells Are Put Together Chapter 4 The Cell • _________ unit of life • Can survive on its own (or has potential to do so) • Is highly organized • Senses and responds to environment • Has potential to reproduce Structure of Cells All start out life with: Two types: – _______ ________ – Prokaryotic – Region where ____ is stored – _________ – _________ 1 Why Are Cells So Small? • _______-__-______ ratio • The bigger a cell is, the less surface area there is per unit volume • Above a certain size, material cannot be moved in or out of cell fast enough Surface-to-Volume Ratio Early Discoveries • Mid 1600s - Robert Hooke observed and described cells in cork • Late 1600s - Antony van Leeuwenhoek observed sperm, microorganisms • 1820s - Robert Brown observed and named nucleus in plant cells 2 Cell Theory 1) Every organism is composed of one or more cells 2) Cell is smallest unit having properties of life 3) Continuity of life arises from growth and division of single cells Lipid Bilayer • Main component of cell membranes • Gives the membrane its _____ properties • ____ layers of__________ 3 Fluid Mosaic Model • Membrane is a mosaic of – Phospholipids – Glycolipids – Sterols – Proteins Membrane Proteins • Adhesion proteins • Communication proteins • Receptor proteins • Recognition proteins Prokaryotic Cells • __________ and ____________ • DNA is ____ enclosed in nucleus • Generally the smallest, simplest cells • ___ _________ 4 Prokaryotic Structure bacterial flagellum pilus plasma membrane bacterial flagellum Most prokaryotic cells have a cell wall outside the plasma membrane, and many have a thick, jellylike capsule around the wall. cytoplasm, with ribosomes DNA in nucleoid region Eukaryotic Cells • Have a ______ and other organelles • Eukaryotic organisms – Plants – ________ – Protistans – _______ Functions of __________ • Keeps the DNA molecules of eukaryotic cells separated from metabolic machinery of cytoplasm • Makes it easier to organize DNA and to copy it before parent cells divide into daughter cells 5 Animal Cell Features NUCLEUS CYTOSKELETON RIBOSOMES ROUGH ER MITOCHONDRION SMOOTH ER CENTRIOLES GOLGI BODY LYSOSOME PLASMA MEMBRANE Nuclear Envelope • Pores span bilayer one of two lipid bilayers (facing nucleoplasm) nuclear pore (protein complex that spans both lipid bilayers) one of two lipid bilayers (facing nucleoplasm) NUCLEAR ENVELOPE Endomembrane System • Group of related organelles in which lipids are assembled and new polypeptide chains are modified • Products are sorted and shipped to various destinations 6 Components of Endomembrane System _____________ ___________ ________ ________ Vesicles Endoplasmic Reticulum • In animal cells, continuous with nuclear membrane • Extends throughout cytoplasm • Two regions: _______ & ________ Rough ER • Arranged into flattened sacs • ________ on surface give it a rough appearance • Cells that specialize in secreting proteins have lots of rough ER 7 Smooth ER • A series of interconnected ________ • No ribosomes on surface • Lipids assembled inside tubules • Sarcoplasmic reticulum of muscle is a specialized form Golgi Bodies • Put finishing touches on proteins and lipids that arrive from ER • Package finished material for shipment to final destinations • Material arrives and leaves in __________ Vesicles • Membranous _____ that move through the cytoplasm • Lysosomes • Peroxisomes 8 Mitochondria • ATP-producing ___________ • Double-membrane system • Outer membrane faces cytoplasm • Inner membrane folds back on itself • ATP-making machinery is embedded in the inner mitochondrial membrane Plant Cell Features CELL WALL CHLOROPLAST CENTRAL VACUOLE NUCLEUS CYTOSKELETON RIBOSOMES ROUGH ER MITOCHONDRION SMOOTH ER PLASMODESMA GOLGI BODY PLASMA MEMBRANE LYSOSOMELIKE VESICLE Chloroplasts Convert sunlight energy to ATP through ________________ 9 Structure of a Chloroplast • Two outer membranes around semifluid interior (stroma) – bathes inner membrane • Often, this single membrane is folded back on itself as a series of stacked, flattened disks • Each stack is called a _________, which contains __________ and other substances involved in photosynthesis Like Bacteria? • Both ___________ and ___________ resemble bacteria • Have own DNA, RNA, and ribosomes Cytoskeleton • Present in all eukaryotic cells • Basis for cell ______ and internal organization • Allows organelle movement within cells and, in some cases, cell motility 10 Cytoskeletal Elements intermediate filament microtubule microfilament Microtubules • _________ elements • Composed of the protein tubulin • Involved in shape, motility, cell division 11 Microfilaments • _________ cytoskeletal elements • Composed of the protein actin • Take part in movement, formation and maintenance of cell shape Intermediate Filaments • Present only in animal cells of certain tissues • Most stable cytoskeletal elements Mechanisms of Movement • Length of microtubules or microfilaments can change • Parallel rows of microtubules or microfilaments actively slide in a specific direction • Microtubules or microfilaments can move organelles to different parts of cell 12 Flagella and Cilia • Structures for cell motility spokes, rings of connective system central sheath one central pair of microtubules • 9+2 arrangement of microtubules plasma membrane one of nine pairs of microtubules with dynein arms down their length microtubules near base of flagellum or cilium plasma membrane basal body (embedded in the cytoplasm) Amoeboid movement • Some free-living cells, such as amoebas, form pseudopods (“______ _____”) • These temporary, irregular lobes project from the cell and function in locomotion and prey capture • Pseudopods move as microfilaments elongate inside them – motor proteins attached to the microfilaments drag the plasma membrane with them ____ ____ • Structural component that wraps around the plasma membrane • Occurs in plants, some fungi, some protistans Plasma membrane Primary cell wall of a young plant 13 Plant ______ • Cell secretions and waxes accumulate at plant cell surface • Semi-transparent • Restricts ______ loss 14