Transcript Cellsx
CELLS Chapter 4 p.57-82 Chapter 4 Outline - Cells 2 Cell Theory Cell Size Prokaryotic Cells Eukaryotic Cells Organelles Nucleus Endomembrane System Cytoskeleton Centrioles, Cilia, and Flagella Cell Theory 3 Originated from the work of biologists in 1838 and 1850 States that: All organisms are composed of cells All cells come only from preexisting cells Smallest unit of life Sizes of Living Things 4 Figure 4A Microscopy and Cheek Cells 6 Cell Size 7 Most much smaller than one millimeter (mm) Some as small as one micrometer (mm) Size restricted by Surface/Volume (S/V) ratio Surface is membrane, across which cell acquires nutrients and expels wastes Volume is living cytoplasm, which demands nutrients and produces wastes As cell grows, volume increases faster than surface Cells specialized in absorption modified to greatly increase surface area per unit volume Prokaryotic Cells:Domains 8 Lack a membrane-bound nucleus Structurally simple Two domains: Bacteria Three Shapes Bacillus (rod) Coccus (spherical) Spirilla (spiral) Archaea Live in extreme habitats Shapes of Bacterial Cells 9 Prokaryotic Cells: Visual Summary 10 Prokaryotic Cells:The Envelope 11 Cell Envelopes Glycocalyx Layer of polysaccharides outside cell wall May be slimy and easily removed, or Well organized and resistant to removal (capsule) Cell wall Plasma Like membrane in eukaryotes Form internal pouches (mesosomes) Prokaryotic Cells:Cytoplasm & Appendages 12 Cytoplasm Semifluid solution Bounded by plasma membrane Contains inclusion bodies – Stored granules of various substances Appendages Flagella – Provide motility Fimbriae – small, bristle-like fibers that sprout from the cell surface Sex pili – rigid tubular structures used to pass DNA from cell to cell Eukaryotic Cells 13 Domain Eukarya Protists Fungi Plants Animals Cells contain: Membrane-bound nucleus Specialized organelles Plasma membrane Eukaryotic Cells :Organelles 14 Compartmentalization: Allows eukaryotic cells to be larger than prokaryotic cells Isolates reactions from others Two classes: Endomembrane system: Organelles that communicate with one another via membrane channels Via small vesicles Energy related organelles Mitochondria & chloroplasts Basically independent & self-sufficient 15 Hypothesized Origin of Eukaryotic Cells Figure 4.6a Figure 4.7a Nucleus 18 Command center of cell, usually near center Separated from cytoplasm by nuclear envelope Consists of double layer of membrane Nuclear pores permit exchange between nucleoplasm & cytoplasm Contains chromatin in semifluid nucleoplasm Chromatin contains DNA of genes Condenses to form chromosomes Dark nucleolus composed of rRNA Produces subunits of ribosomes Anatomy of the Nucleus 19 Ribosomes 20 Serve in protein synthesis Composed of rRNA Consists of a large subunit and a small subunit Subunits made in nucleolus May be located: On the endoplasmic reticulum (thereby making it “rough”), or Free in the cytoplasm, either singly or in groups called polyribosomes Endomembrane System 21 Restrict enzymatic reactions to specific compartments within cell Consists of: Nuclear envelope Membranes of endoplasmic reticulum Golgi apparatus Vesicles Several types Transport materials between organelles of system Endomembrane System: The Endoplasmic Reticulum 22 Rough ER Studded with ribosomes on cytoplasmic side Protein anabolism Synthesizes proteins Modifies proteins Adds sugar to protein Results in glycoproteins Smooth ER No ribosomes Synthesis of lipids Peroxisomes 23 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 Vacuoles 24 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 Energy-Related Organelles: Chloroplast Structure 25 Bounded by double membrane Inner membrane infolded Forms disc-like thylakoids, which are stacked to form grana Suspended in semi-fluid stroma Green due to chlorophyll Green photosynthetic pigment Found ONLY in inner membranes of chloroplast Energy-Related Organelles: Chloroplasts 26 Captures light energy to drive cellular machinery Photosynthesis Synthesizes Makes carbohydrates from CO2 & H2O own food using CO2 as only carbon source Energy-poor compounds compounds converted to enery rich Organelles: Chloroplast Structure 27 Energy-Related Organelles: Mitochondria 28 Bounded by double membrane Cristae – Infoldings of inner membrane that encloses matrix Matrix – Inner semifluid containing respiratory enzymes Involved in cellular respiration Produce most of ATP utilized by the cell Organelles: Mitochondrial Structure 29 The Cytoskeleton 30 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 Figure 4.18 Microtubular Arrays:Centrioles 32 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 Microtubular arrays: Cilia and Flagella 33 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 Table 4.1 Chapter review assignment I. Complete the Testing Yourself section of the chapter review on page 81-82 (#1-15) II. Discuss the bioethical issue about stem cells. III. Find all vocabulary words in your notes. I. If a word was not defined in the notes, define it here. II. Answer the matching questions a. – e.