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Cells

1. Theory and Structure2. Animal Cells

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Cell Theory1.All organisms are composed of one or more

cells2.The cell is the basic unit of organization

(structure and function) of organisms3.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 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

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

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

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