Bio108 lec1

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  • 7/31/2019 Bio108 lec1


    Cell biology(formerly cytology, from the Greek kytos,"container") is an academic discipline that studies cells

    theirphysiological properties

    their structure,

    the organelles they contain

    interactions with their environment,

    theirlife cycle, division and death.

    Cellbasic unit of life structurally and functionally.History:

    a. Robert Hooke (1665)using his microscope discoverscells in cork

    b. Schleiden ; Schwann and VirchowCell theory:

    1. All organisms are composed of one or morecells

    2. The cell is the structural unit of life3. Cells can arise only by division from

    preexisting cells
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    Fundamental properties shared by all cells: (conserved throughout evolution)

    1. all cells employ DNA as their genetic material2. surrounded by plasma membrane3. use the same basic mechanisms for energy metabolism

    Organisms:1. Unicellular (eg. bacteria, amoebas & yeasts) capable of independent

    self-replication2. Multicellular(eg. Humans)- composed of collection of cells w/c fxns in

    a coordinated manner w/ diff cells specialized to performparticular tasks.

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    Two Main Classes of Cells:

    a. Prokaryotic cells no nucleus- simpler structure (bacteria)

    b. Eukaryotic cells - contain nucleus-more complex structure(protists, fungi,

    plants & animals)

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    Prokaryotes Eukaryotes

    Typical organisms bacteria, archaea protists, fungi, plants, animals

    Typical size ~ 1-10 m~ 10-100 m (sperm cells, apart from

    the tail, are smaller)Type ofnucleus nucleoid region; no real nucleus real nucleus with double membrane

    DNA circular (usually)linear molecules (chromosomes)with histoneproteins

    RNA-/protein-synthesis coupled in cytoplasmRNA-synthesis inside the nucleusprotein synthesis in cytoplasm

    Ribosomes 50S+30S 60S+40S

    Cytoplasmatic structure very few structureshighly structured byendomembranes and a cytoskeleton

    Cell movement flagella made offlagellinflagella and cilia containingmicrotubules; lamellipodia andfilopodia containing actin

    Mitochondria noneone to several thousand (though

    some lack mitochondria)Chloroplasts none in algae and plants

    Organization usually single cellssingle cells, colonies, highermulticellular organisms withspecialized cells

    Cell division Binary fission (simple division)Mitosis (fission or budding)Meiosis

    DNA content (base pairs) 1 106 to 5 106 1.5 107 to 5 109

    Table 1: Comparison of features of prokaryotic and eukaryotic cells
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    Fig.1.1.Average_prokaryote_cell-_en.svg (SVG

    file, nominally 494 402 pixels, file size: 135KB)
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    Fig1.2.Diagram of a typical animal (eukaryotic) cell, showing subcellular components.Organelles:(1) nucleolus(2) nucleus

    (3) ribosome(4)vesicle(5) rough endoplasmic reticulum (ER)(6) Golgi apparatus(7) Cytoskeleton(8) smooth endoplasmic reticulum(9) mitochondria(10)vacuole(11) cytoplasm

    (12) lysosome(13) centrioles within centrosome
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    Fig.1.3.Diagram of a typical plant cell
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    the First Cell:

    -all present day cells (both prokaryotes & eukaryotes) descended

    from a single ancestor. The 1st

    cell is thought to have arisen at least 3.8 Byears ago as a result of enclosure of self-replicating RNA in a phospholipidmembrane (RNA world hypothesis)

    Present-Day Prokaryotes-divided into two groups: the archaebacteria and the eubacteria which

    diverged early in evolution

    Eukaryotic Cells-thought to have evolved from symbiotic associations of

    prokaryotes (ENDOSYMBIOSIS)

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    A large anaerobic, heterotrophic prokaryote engulfs a small aerobic prokaryote

    The aerobic endosymbiont has evolved into a mitochondrion

    A portion of the plasma membrane has invaginated and evolved into anuclear envelope and endoplasmic reticulum

    (primitive eukaryote)

    Nonphotosynthetic protist, fungal,animal cells

    Engulfs a photosynthetic prokaryote

    Evolve into a chloroplast

    Algal & plant cells

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    Fig.1.4. Time scale of evolution The scale indicates the approximate times at which

    some of the major events in the evolution of cells are thought to have occurred.

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    Figure 1.5. Generation of metabolic energy Glycolysis is the anaerobic breakdown of glucose to lactic acid.

    Photosynthesis utilizes energy from sunlight to drive the synthesis of glucose from CO2

    and H2O, with the release

    of O2

    as a by-product. The O2

    released by photosynthesis is used in oxidative metabolism, in which glucose is

    broken down to CO2 a