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CHAPTER 7. A TOUR OF THE CELL OVERVIEW. A. MICROSCOPES PROVIDE WINDOWS TO THE WORLD OF THE CELL. I. HOW WE STUDY CELLS. II. A PANORAMIC VIEW OF THE CELL. A. PROKARYOTIC AND EUKARYOTIC CELLS DIFFER IN SIZE AND COMPLEXITY ALL CELLS ARE BOUNDED BY PLASMA MEMBRANE
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CHAPTER 7 A TOUR OF THE CELL OVERVIEW
A. MICROSCOPES PROVIDE WINDOWS TO THE WORLD OF THE CELL I. HOW WE STUDY CELLS
II. A PANORAMIC VIEW OF THE CELL • A. PROKARYOTIC AND EUKARYOTIC CELLS DIFFER IN SIZE AND COMPLEXITY • ALL CELLS ARE BOUNDED BY PLASMA MEMBRANE • PROKARYOTIC: CELLS WITHOUT NUCLEI OR OTHER MEMBRANE ENCLOSED ORGANELLES. Ex. BACTERIA AND ARCHAEBACTERIA • EUKARYOTIC: CELLS WITH MEMBRANE ENCLOSED NUCLEI AND OTHER SPECIALIZED ORGANELLES IN THEIR CYTOPLASM Ex. ALL OTHER ORGANISMS
THE PLASMA MEMBRANE: FUNCTIONS AS A SELECTIVE BARRIER (FIG. 7.6) B. INTERNAL MEMBRANES COMPARTMENTALIZE THE FUNCTIONS OF A EUKARYOTIC CELL
THERE ARE TWO MAIN TYPES OF EUKARYOTIC CELLS(FIG. 7.7 ANIMAL)
III. THE NUCLEUS AND RIBOSOMES • THE NUCLEUS CONTAINS A EUKARYOTIC CELL’S GENETIC LIBRARY • DNA IS ORGANIZED WITH PROTEINS INTO CHROMOSOMES, WHICH EXIST AS CHROMATIN IN NONDIVIDING CELLS • MACROMOLECULES PASS BETWEEN NUCLEUS AND CYTOPLASM THROUGH PORES IN THE NUCLEAR ENVELOPE
FREE RIBOSOMES IN THE CYTOSOL, AND BOUND RIBOSOMES ON THE OUTSIDE OF THE ENDOPLASMIC RETICULUM, SYNTHESIZE PROTEINS(FIG. 7.10) B. RIBOSOMES BUILD A CELL’S PROTEINS
IV. THE ENDOMEMBRANE SYSTEM • DEFINITION: THE COLLECTION OF MEMBRANES INSIDE AND AROUND A EUKARYOTIC CELL, RELATED EITHER THROUGH DIRECT PHYSICAL CONTACT OR BY THE TRANSFER OF MEMBRANOUS VESICLES
A. THE ENDOPLASMIC RETICULUM MANUFACTURES MEMBRANES AND PERFORMS MANY OTHER BIOSYNTHETIC FUNCTIONS • CONTINOUS WITH THE NUCLEAR ENVELOPE, THE ENDOPLASMIC RETICULUM (ER) IS A NETWORK OF CISTERNAE. • CISTERNAE: MEMBRANE ENCLOSED COMPARTMENTS. • TRANSPORT VESSICLE: DISTRIBUTES ER’S PRODUCTS • TYPES OF ENDOPLASMIC RETICULUM • SMOOTH ER: LACKS RIBOSOMES; SYNTHESIZES STEROIDS, METABOLIZES CARBS. • ROUGH ER: HAS BOUND RIBOSOMES; PRODUCES PROTEINS
B. THE GOLGI APPARATUS FINISHES, SORTS, AND SHIPS CELL PRODUCTS • STACKS OF SEPARATE CISTERNAE MAKE UP THE GOLGI • PARTS OF GOLGI APPARATUS • CIS FACE: RECEIVES SECRETORY PROTEINS FROM THE ER IN TRANSPORT VESSICLES • TRANS FACE: MODIFIES, SORTS AND RELEASES PROTEINS IN TRANSPORT VESSICLES
LYSOSOMES ARE MEMBRANOUS SACS OF HYDROLYTIC ENZYMES FUNCTION: BREAKDOWN CELL MACROMOLECULES FOR RECYCLING(7.13) C. LYSOSOMES ARE DIGESTIVE COMPARTMENTS
A PLANT CELL’S CENTRAL VACUOLE FUNCTIONS IN STORAGE, WASTE DISPOSAL, CELL GROWTH, AND PROTECTION D. VACUOLES HAVE DIVERSE FUNCTIONS IN CELL MAINTENANCE
V. OTHER MEMBRANOUS ORGANELLES • A. MITOCHONDRIA AND CHLOROPLASTS ARE THE MAIN ENERGY TRANSFORMERS OF CELLS • MITOCHONDRIA: SITE OF CELLULAR RESPIRATION IN EUKARYOTES • STRUCTURE: OUTER MEMBRANE AND INNER MEMBRANE FOLDED INTO CRISTAE
STRUCTURE: TWO MEMBRANES SURROUND THE FLUID STROMA, WHICH CONTAINS THYLAKOIKS, OFTEN STACKED IN GRANA DEFINITIONS: CRISTAE: AN INFOLDING OF THE INNER MEMBRANE OF A MITOCHONDRION, THAT HOUSES THE ENZYME CATALYZING THE SYNTHESIS OF ATP PLASTIDS: ONE OF A FAMILY OF CLOSELY RELATED PLANT ORGANELLES, INCLUDIND CHLOROPLASTS, CHROMOPLASTS, AND AMYLOPLASTS STROMA: THE FLUID OF THE CHLOROPLAST SURROUNDING THE THYLAKOID MEMBRANE THYLAKOIDS: A FLATTENED MEMBRANE SAC INSIDE THE CHLOROPLAST GRANA: A STACKED PORTION OF THE THYLAKOID MEMBRANE IN THE CHLOROPLAST CHLOROPLASTS: A TYPE OF PLASTID, CONTAINS CHLOROPHYLL AND OTHER PIGMENTS, WHICH FUNCTION IN PHOTOSYNTHESIS
PEROXISOMES: ORGANELLES THAT BREAK DOWN VARIOUS SUBSTANCES; PRODUCE H202 AS WASTE C. PEROXISOMES CONSUME OXYGEN IN VARIOUS METABOLIC FUNCTIONS
VI. THE CYTOSKELETON • A. PROVIDES STRUCTURAL SUPPORT TO CELLS FOR CELL MOTILITY AND REGULATION • STRUCTURE: MADE OF MICROTUBULES, MICROFILAMENTS, AND INTERMEDIATE FILAMENTS
MICROTUBULES: HOLLOW CYLINDERS; SHAPE THE CELL, GUIDE MOVEMENT OF ORGANELLES, AID CHROMOSOME SEPARATION IN DIVIDING CELLS
CILIA AND FLAGELLA: MOTILE APPENDAGES CONTAINING MICROTUBULES DOUBLETS
INTERMEDIATE FILAMENTS: SUPPORT CELL SHAPE AND ORGANELLES IN PLACE MICROFILAMENTS: THIN RODS BUILT FROM THE PROTEIN ACTIN; FUNCTION IN MUSCLE CONTRACTION
VII. CELL SURFACES AND JUNCTIONS • A. PLANT CELLS ARE ENCASED BY CELL WALLS • PLANT CELL WALLS ARE COMPOSED OF CELLULOSE FIBERS EMBEDDED IN OTHER POLYSACCHARIDES AND PROTEIN
B. INTERCELLULAR JUNCTIONS HELP INTEGRATE CELLS INTO HIGHER LEVELS OF STRUCTURE AND FUNCTION • IN PLANTS • PLASMODESMATA: CYTOPLASMIC CHANNELS THAT PASS THROUGH ADJOINING CELL WALLS • IN ANIMALS • TIGHT JUNCTIONS: INTERCELLULAR JUNCTION THAT PREVENTS LEAKAGE OF MATERIAL BETWEEN CELLS • DESMOSOMES: FUNCTIONS AS AN ANCHOR; ACT AS SPOT WELDS TO HOLD TOGETHER TISSUES THAT UNDERGO CONSIDERABLE STRESS EX. SKIN/ HEART TISSUE • GAP JUNCTIONS: ALLOWS THE PASSAGE OF MATERIAL OR CURRENT BETWEEN CELLS (IONS AND SMALL MOLECULES) ; PREVENTS CYTOPLASMS OF EACH CELL FROM MIXING