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Cells
1. Theory and Structure
2. Animal Cells
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Cell Theory
1.All organisms are composed of one or more
cells
2.The cell is the basic unit of organization
(structure and function) of organisms
3.All cells come from pre-existing cells
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Exceptions to the Cell Theory
• Electron microscope reveals that
mitochondria and chloroplasts can
reproduce themselves
• Not all living things are composed of
cytoplasm and a nucleus surrounded by a
cell membrane(Examples: skeletal tissue,
slime mold)
• Virus particles can reproduce
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Cell Organelles
• Membrane-bound cell structures that
perform one or more functions
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Cytoplasm
• Fluid protoplasm (living matter) that fills
the cell and contains the organelles
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Cytoskeleton
• Network of thin, hollow
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tubes and fibers
Provides support and shape
Composed of microtubules
(thin, hollow cylinders
composed of protein) and
microfilaments (thin protein
fibers)
Microtubules – support
Microfilaments – aid in cell
movement
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Nucleus
• EUKARYOTES
• Control center
• Contains genetic
material (DNA)
• Pores in the nuclear
membrane permit
passage of certain
chemicals into
cytoplasm
• Contains chromosomes
(contain code that
guides all cell activities)
• Chromatin threads
(DNA tangles) form the
chromosomes
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Nucleolus
• Found in nucleus
• Produces ribosomes
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Plasma Membrane
• Boundary between cell and external environment that
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controls movement of what goes into and out of the cell
( Oxygen and nutrients in; waste products and excess
water out)
Functions to identify the cell
Functions in communication between cells
“Selectively permeable” (semi permeable)
Lipid bilayer in which large protein molecules float
(Cholesterol is a component)
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Pinocytic Vesicles
• Sac-like enfolding of the plasma membrane
• Small particles that cannot pass through the
plasma membrane may be taken into the cell
• Pinocytosis- “to drink”
• Phagocytosis- “to eat” ( a protective mechanism)
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Endoplasmic Reticulum
• Assembly and transport of
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proteins
Folded membrane with a
network of interconnected
departments
Connects nuclear membrane
with plasma membrane
Rough ER – attached
ribosomes
Smooth ER – no ribosomes,
makes new membranes for
the cell
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Ribosomes
• “Protein factories” (Site of protein
synthesis)
• Has a subunit made of RNA
• Free in cytoplasm or attached to
endoplasmic reticulum
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Golgi Apparatus
• Closely stacked flattened sacs
• Synthesizes, packages, and secretes cell products
• “Carbohydrate producing and packaging factory” (Makes
mucus)
• Produces lysosomes
• Packages and ships proteins made by the cell either out of
the cell or to another part of the cell
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Lysosomes
• Round organelles
that contain digestive
enzymes
• Digests excess or
worn-out cell parts,
food particles,
invading
viruses/bacteria
• “Suicide-sacs” –
sometimes digest
cells that contain
lysosomes
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Mitochondria
• Outer membrane and an inner membrane
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with long, narrow folds called cristae
“Powerhouse of the cell”
“Survival of the cell”
Respiration: food molecules are broken
down to release energy
Mitochondria-energy-ATP
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Cilia and Flagella
• Movement
• Cilia- short hair-like projection of plasma
membrane that have beating motion (found
in lining of wind pipe)
• Flagella- long, whip-like projections that
lash back and forth ( found in sperm cells )
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Chromatin and Chromosomes
• Chromatin granules in the nucleus are
thread-like structures made of DNA
• Chromosomes are tightly coiled DNA
molecules (This happens during cell
division.)
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Centrioles/Centrosomes
• Most animal cells have centrioles, cylinders
containing tiny tubules, that appear to play an
important role in mitosis (cell division for growth
and repair)
• Centrosomes also play a role in cell division
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