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Cellular Structure
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Cell Theory The cell theory is the unifying theme
in biology because it emphasizes the similarity of all living things.All organisms are composed of one or
more cells.Cells are the smallest living units of all
living organisms.Cells arise only by division of a
previously existing cell.
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Cell Characteristics The basic processes necessary for living things
to survive are the same for a single cell as they are for a more complex organism. A single-celled organism has to conduct all
life processes by itself. A multi-cellular organism has groups of cells
that specialize to perform specific functions. Small cells function more efficiently than
large cells because they have a higher surface-area-to-volume ratio and therefore shorter diffusion time.
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Examples of Cells
Amoeba Proteus
Plant Stem
Red Blood Cell
Nerve Cell
Bacteria
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Cells and Cell Size
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All cells contain Genetic material
single circular molecule of DNA in prokaryotes
double helix located in nucleus in eukaryotes
Cytoplasm jelly-like substance that fills the cells interior
Plasma membrane encloses the cell Separates the cell interior phospholipid bilayer
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Cell Types
Cell structure is one of the ways in which organisms differ from each other.2 Types of Cells
•Prokaryote – Greek words for pre-nucleus
•Eukaryote – Greek words for true-nucleus
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Prokaryotic Cells Earth’s first cells
were prokaryotes.
The simplest life forms are the prokaryotes.
Prokaryotic cells exist in two major forms: eubacteria and archaebacteria.
ALL are UNICELLULAR
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Prokaryotic Cells
Prokaryotes are the Earth’s most abundant inhabitants. They can survive in a wide range of environments and obtain energy in a variety of ways.
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Prokaryotic Cells
Prokaryotes are cells that
lack a nucleus and membrane bound organelles.
cause disease and infection
grow and divide very rapidly
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Prokaryotic Cells Flagella
Thread like structures used for locomotionFlagellum - singular Bacterial cell wall
Flagellum
Rotarymotor
Sheath
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Eukaryotic Cells
Contain organelles surrounded by membranes Most living organisms
Plant Animal
http://library.thinkquest.org/C004535/eukaryotic_cells.html
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Eukaryote
•Eukaryotes arose from prokaryotes and developed into larger more complex organisms.
•Eukaryotes are cells that contain a nucleus and organelles surrounded by a membrane
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Two Theories of Origin•Autogenic vs. Endosymbiotic
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Eukaryote
•Can be both unicellular or multi-cellular
•Examples of eukaryotes are:
•All fungi, plant, and animal cells
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http://web.jjay.cuny.edu/~acarpi/NSC/images/cell.gif
17http://waynesword.palomar.edu/images/plant3.gif
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Summary of differences!
Prokaryotic Cells Eukaryotic cells
small cells 1um-10um) larger cells (10 um-100um)
always unicellular often multicellular
no nucleus or any membrane-bound organelles in cytosol
always have nucleus and other membrane-bound organelles in
cytosol
DNA is circular, without proteinsCalled a nucleoid
DNA is linear and associated with proteins to form chromatin
ribosomes are small (70S) ribosomes are large (80S)
no cytoskeleton always has a cytoskeleton
cell division is by binary fission cell division is by mitosis or meiosis
reproduction is always asexual reproduction is asexual or sexual
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Nucleus
The Control Center Stores genetic
material (DNA) Double membrane
with pores Largest organelle
Nucleolus – dark center where ribrosomes are made
Chromatin – complex of DNA and protein that makes up chromosomes
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Cytoskeleton Long slender protein tubes and fibers that
extend from the nucleus to the plasma membrane.
Provide the interior framework of an animal cell.
The cytoskeleton contains three types of elements responsible for cell shape, movement within the cell, and movement of the cell:
Actin filaments MicrotubulesIntermediate filaments
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Cytoskeleton Actin filaments
Muscle fibers used in locomotion
Actin/myosinShape – expand
and contract
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MicrotubulesTubulinhollowTransportatio
n system – railroad tracks that move•Protein
complexes•RNA
Cytoskeleton
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Cytoskeleton
MicrotubulesFlagellumSpindle fibres
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Cytoskeleton Intermediate filaments
Frame for confinementAnchors proteins together so they can
work as a complexSolid
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Cytoskeleton
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o Found in ALL cells
o Membrane that encloses the cytoplasm.
Cell Membrane
o Called plasma membrane
o Controls what enters and leaves the cell
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Cell MembraneFluid Mosaic Model
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Ribosomes
Ribosomes are RNA-protein complexes composed of two subunits that join and attach to messenger RNA.site of protein synthesisAlone in cytoplasm
• makes proteins for use within the cellAttached to ER
• makes proteins for export out of the cell
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Endoplasmic ReticulumER –Made up of a lipid bilayer
with embedded proteins•Rough ER - studded with ribosomes
•Site of protein synthesis and processing
•Smooth ER - lacks ribosomes
•Site of synthesis of phospholipids and the packaging of proteins into vesicles
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Endoplasmic reticulum
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Golgi apparatusGolgi bodies
•Stacked flattened sacks
•Site where cell products are packaged for export
• Proteins are modified by being combined with fats or carbohydrates
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Golgi apparatus
Vesiclebuddingfrom roughendoplasmicreticulum
Fusionof vesiclewith Golgiapparatus
Migratingtransportvesicle
Protein
Proteins
Transportvesicle
Golgiapparatus
Ribosome
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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Lysosomes
Vesicles produced by the Golgi apparatus.
Lysosomes contain digestive enzymes and are involved in intracellular digestion of food particles, disease causing bacteria and worn out cell parts
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Organelles With DNA
Mitochondria site of cell
respiration
Chloroplastssite of
photosynthesis
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Mitochondria
Very active cells have more mitochondria
Has its own DNA Found in both plants and animals
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Chloroplasts
• Chloroplasts are larger and more complex than mitochondria
•Contain green pigment called chlorophyll that absorbs sunlight in the first step of photosynthesis
•Found ONLY in PLANTS
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Chloroplasts
•Thylakoids are the site of photosynthesis
•Grana – stacked thylakoids
•Stroma – fluid around the grana
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Cell Wall
•provides support
•Found in PLANT cells only
•Made from cellulose
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Vacuoles
Found in PLANT and ANiMAL cells The vacuole acts a container, storing
water and dissolved particles Plants have a large central vacuole
for water storageTurgor Pressure
Unicellular animals can use contractile vacuoles for movement
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Plant vs. Animal Cells
PLANT CELL
ANIMAL CELL
Cell membraneMitochondria
Golgi apparatusNucleus
CytoskeletonRibosomes
Endoplasmic reticulum
Lysosomes
HAVE:Cell Wall
LARGE vacuolesChloroplasts
DO NOT HAVE:Cell Wall
LARGE vacuolesChloroplasts
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Eukaryotic Plant Cell
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Eukaryotic Animal Cell
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Endosymbiosis Endosymbiosis theory suggests that
eukaryotes arose from a symbiotic relationship between various prokaryotes.
Heterotrophic bacteria became mitochondria.
Cyanobacteria became chloroplasts.
Host cell was a large eukaryotic cell.
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Cell Differentiation Cell specialization occurs during the
development of a multi-cellular organism. The genetic information necessary for all
cellular functions remains in each cell but may not be used.
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Cell Humor
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