Ch04 Lecture
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Transcript of Ch04 Lecture
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Cell Structure and Function
Chapter 4
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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
Early Discoveries
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Developing Cell Theory
Matthias Schleiden
Theodor Schwann
Rudolf Virchow
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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
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Smallest unit of life Can survive on its own or has potential
to do so Is highly organized for metabolism Senses and responds to environment Has potential to reproduce
Cell
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Structure of Cells
All start out life with: Plasma membrane Region where DNA
is stored Cytoplasm
Two types: Prokaryotic Eukaryotic
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Main component of cell membranes Gives the membrane its fluid properties Two layers of phospholipids
Lipid Bilayer
one layerof lipids
one layerof lipids
Figure 4.3Page 56
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Membrane Proteins
Protein pump across
bilayer
Protein channel
across bilayer
Protein pump
Recognition protein
Receptor protein
extracellular environment
cytoplasm
lipid bilayer
Figure 4.4Page 57
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Why Are Cells So Small?
Surface-to-volume 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
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Create detailed images of something that is otherwise too small to see
Light microscopes Simple or compound
Electron microscopes Transmission EM or Scanning EM
Microscopes
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Limitations of Light Microscopy
Wavelengths of light are 400-750 nm
If a structure is less than one-half of a wavelength long, it will not be visible
Light microscopes can resolve objects down to about 200 nm in size
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Electron Microscopy
Uses streams of accelerated electrons rather than light
Electrons are focused by magnets rather than glass lenses
Can resolve structures down to 0.5 nm
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Eukaryotic Cells
Have a nucleus and other organelles
Eukaryotic organisms Plants Animals Protistans Fungi
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Animal Cell Features
Plasma membrane Nucleus Ribosomes Endoplasmic
reticulum Golgi body Vesicles Mitochondria Cytoskeleton Figure 4.10b
Page 61
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Plant Cell Features
Cell wall Central vacuole Chloroplast
Plasma membrane Nucleus Ribosomes Endoplasmic
reticulum Golgi body Vesicles Mitochondria Cytoskeleton Figure 4.10a
Page 61
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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
Functions of Nucleus
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Components of Nucleus
nuclear envelope
nucleoplasm
nucleolus
chromatin
Figure 4.11bPage 62
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Nuclear Envelope
Two outer membranes (lipid bilayers) Innermost surface has DNA attachment sites
Nuclear pore bilayer facing cytoplasm Nuclear envelope
bilayer facing nucleoplasm
Figure 4.12bPage 63
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Group of related organelles in which lipids are assembled and new polypeptide chains are modified
Products are sorted and shipped to various destinations
Cytomembrane System
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Components of Cytomembrane System
Endoplasmic reticulum
Golgi bodies
Vesicles
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Endoplasmic Reticulum
In animal cells, continuous with nuclear membrane
Extends throughout cytoplasm
Two regions - rough and smooth
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Golgi Body Puts finishing touches on proteins and
lipids that arrive from ER Packages finished material for shipment to
final destinations Material arrives and leaves in vesicles
budding vesicle
Figure 4.15Page 65
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Vesicles Membranous sacs that
move through cytoplasm
Lysosomes
Peroxisomes
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ATP-producing powerhouses
Membranes form two distinct
compartments
ATP-making machinery embedded
in inner mitochondrial membrane
Mitochondria
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Mitochondrial Origins
Mitochondria resemble bacteria
Have own DNA, ribosomes
Divide on their own May have evolved from ancient bacteria
that were engulfed but not digested
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Plastids
Central Vacuole
Specialized Plant Organelles
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Chloroplasts
Convert sunlight energy to ATP through photosynthesis
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Other Plastids
Chromoplasts No chlorophyll Abundance of carotenoids Color fruits and flowers red to yellow
Amyloplasts No pigments Store starch
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Present in all eukaryotic cells
Basis for cell shape and internal organization
Allows organelle movement within cells and, in some cases, cell motility
Cytoskeleton
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Cytoskeletal Elements
microtubule
microfilament
intermediatefilament
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Microtubules
Largest elements Composed of tubulin Arise from microtubule
organizing centers (MTOCs) Involved in shape, motility,
cell division
Figure 4.21Page 71
tubulinsubunit
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Microfilaments
Thinnest elements
Composed of actin
Take part in movement, formation, and maintenance of cell shape
actinsubunit
Figure 4.21Page 71
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Intermediate Filaments
Only in animal cells of certain tissues
Most stable cytoskeletal elements
Six known groups
onepolypeptidechain
Figure 4.21Page 71
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Motor Proteins
Kinesins and dyneins move along microtubules
Myosins move along microfilaments
kinesin
microtubule
Figure 4.24b, Page 72
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Flagella and Cilia
Structures for cell motility
9 + 2 internal structure
dynein
microtubule
Figure 4.25Page 73
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Plant Cell Walls
Primary cell wall
Secondary cell wall(3 layers)
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Plant Cuticle
Cell secretions and waxes accumulate at plant cell surface
Semitransparent
Restricts water loss
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Matrixes between Animal Cells
Animal cells have no cell walls
Some are surrounded by a matrix of cell secretions and other material
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Cell-to-Cell Junctions
Plants Plasmodesmata
Animals Tight junctions Adhering junctions Gap junctions
plasmodesma
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Animal Cell Junctions
tightjunctions
adhering junction
gapjunction
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Archaebacteria and Eubacteria
DNA is not enclosed in nucleus
Generally the smallest, simplest cells
No organelles
Prokaryotic Cells
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Prokaryotic Structure
DNA
pilus
flagellum
cytoplasm with ribosomes
capsulecell wall
plasma membrane
Cell Structure and FunctionEarly DiscoveriesDeveloping Cell TheoryCell TheoryCellStructure of CellsLipid BilayerMembrane ProteinsWhy Are Cells So Small?MicroscopesLimitations of Light MicroscopyElectron MicroscopyEukaryotic CellsAnimal Cell FeaturesPlant Cell FeaturesFunctions of NucleusComponents of NucleusNuclear EnvelopeCytomembrane SystemComponents of Cytomembrane SystemEndoplasmic ReticulumGolgi BodyVesiclesMitochondriaMitochondrial OriginsSpecialized Plant OrganellesChloroplastsOther PlastidsCytoskeletonCytoskeletal ElementsMicrotubulesMicrofilamentsIntermediate FilamentsMotor ProteinsFlagella and CiliaPlant Cell WallsPlant CuticleMatrixes between Animal CellsCell-to-Cell JunctionsAnimal Cell JunctionsProkaryotic CellsProkaryotic Structure