Theory and Structure Animal Cells

Cell Theory All organisms are composed of one or more cells The cell is the basic unit of organization (structure and function) of organisms All cells come from pre-existing cells

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

Cell Organelles Membrane-bound cell structures that perform one or more functions

Cytoplasm Fluid protoplasm (living matter) that fills the cell and contains the organelles

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

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

Nucleolus Found in nucleus Produces ribosomes

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)

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)

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

Ribosomes “Protein factories” (Site of protein synthesis) Has a subunit made of RNA Free in cytoplasm or attached to endoplasmic reticulum

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

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

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

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 )

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.)

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