Cell Theory - Weeblybiology12-benabo.weebly.com/.../4/4/4/2/4442802/1.cells.pdf1 Cell Biology Cell...
Transcript of Cell Theory - Weeblybiology12-benabo.weebly.com/.../4/4/4/2/4442802/1.cells.pdf1 Cell Biology Cell...
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Cell Biology
Cell Theory &
Cell Structures
a review! �
Cell Theory • refers to the idea that cells are the
basic unit of structure and function of all living things. • Cells are either prokaryotic or eukaryotic
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Prokaryotic (before “nucleus”) • Lacks membrane-
bound nucleus • Single, usually circular
genophore of DNA
• Lacks membrane bound organelles
• Structurally Simple • Metabolically diverse • Adapted to most types
of environments
Eukaryotic (true “nucleus”) • Have a membrane-
bound nucleus • Possess membrane
bound organelles • Structurally complex • May have a cell wall
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Eukaryotic Cells
Cell Theory • All organisms are composed of
one or more cells • Either unicellular or multicellular
Unicellular - Amoeba Multicellular - Polar Bear
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Cell Theory • All cells come from pre-exisiting
cells • Via binary fission, mitosis, or meiosis
Cell Size • Surface Area / Volume Ratio
• Amount of surface area affects the ability to get materials in and out of a cell
• A cells increase in volume, the proportionate amount of surface area decreases
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A basic cell consists of… euk
aryotic
^ !
Nucleus - contains DNA
Cytoplasm - contains organelles (functional units of the cell) - cytoskeleton
Cell Membrane - protects - regulates what enters/exits
Cell Structures (a brief overview)
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The Nucleus - “the boss” • Site of DNA
• Genetic blueprint
• Provides “instructions” that guide cell’s life processes
Nuclear Envelope • Protective double membrane • Regulatory body, perforated with pores
• Continuous with the ER
Nucleoplasm • Nuclear fluid • Rich in chromatin • Form chromosomes during cell division • Site of mRNA (transcription) and tRNA formation
Nucleolus • rRNA synthesis
• Assembly of ribosomes • Site of protein synthesis
• Receives instruction from nucleus
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Ribosomes • Site of protein synthesis (assembly of a.a. into protein) • Two subunits (small and large)
• Consist of rRNA and protein molecules • Found on the ER (Rough ER) • Polysomes - ribosomes that are clumped together, free floating
in cytoplasm • Also found in mitochondria and chloroplasts
• Polyribosomes • Several ribosomes with a single mRNA molecule
• Nuclear Envelope - nuclear pores
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Endomembrane System
• Inner membrane • An internal “highway” within the cell
• Several interrelated membrane bound compartments found in eukaryotic cells • Includes Rough ER, Smooth ER, Golgi
Apparatus
Endoplasmic Reticulum (ER) • Present in all nucleated cells • System of membrane-bound channels in
cytoplasm that serve as routes of transport of materials between various parts of cytoplasm and nucleus
= communication network in the cell
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Rough ER • Processing and modification of proteins
(Translation) • Lined with ribosomes
Smooth ER
• NO ribosomes present • Site of lipid (steroid) synthesis
• Storage and transport
• detoxification
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Golgi Apparatus • System of membranous sacs • Collects, sorts, packages and distributes
materials such as proteins and lipids • Import/export center
EXPORT • Modifies proteins for export out of cell • Forms secretory vesicles
• Exocytosis of proteins (eg. Insulin), lipids (eg. estrogen), waste products
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IMPORT • Forms the lysosome
• Lyse = to break aprt Some = body
• Digestion (hydrolytic) vesicle • Lysosomes contain digestive enzymes: Acid Hydrolase
Digestion of Incoming Nutrients
Autodigestion (Recycling)
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Vacuoles • Membranous sacs that store substances (water,
pigments, toxins) • Helps maintain cell turgidity (shape)
Energy-based Organelles Chloroplast • Site of photosynthesis
Mitochondria • Site of cell respiration
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Chloroplast • A pigment (chlorophyll) filled plastid
• Chlorophyll is located in the thylakoid membranes
• Captures solar energy required for photosynthesis and the production of CHO’s.
• In PLANTS, ALGAE & CYANOBACTERIA only • Site of photosynthesis
Structure: – Double-membrane – Stroma – Grana
§ Thylakoids
Chloroplasts contain: – Their own DNA – Ribosomes – Enzymes
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Mitochondria • Found in all eukaryotic cells (both plants & animals) • Site of cellular respiration
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ATP (Adenosine Triphosphate) • Energy Currency • A nucleotide • Does “work”
Sugar, Fat and Proteins can make ATP!!!
High Energy Bond
Plasma Membrane & Cytoplasm • All cells are surrounded by a cell membrane
• (aka plasma membrane, lipid bilayer, phospholipid bilayer)
• The material inside of a cell is the cytoplasm • The plasma membrane is a semi-
permeable lipid bilayer that regulates what enters / exits a cell
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Fluid Mosaic Model • Contains a variety or “mosaic” of
biological molecules (primarily proteins and lipids)
• Membrane is not solid but “fluid” with phospholipids and proteins that shift
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Cell Wall • Semi-rigid, permeable layer that helps maintain
cell shape and chemical equillibrium • In PLANT cells
• Composed of cellulose
Cytoskeleton • Maintains cell shape • Assists in movement of cell and organelles • Anchors organelles • Three types of macromolecular fibers
• Actin Filaments • Intermediate Filaments • Microtubules
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Actin Filaments • Anchored to plasma membrane • Allows intestinal microvilli to expand and
contract • Found in pseudopods allowing ameoboid
movement • Play role in cell division in animals
Intermediate Filaments • Intermediate in size between actin filaments and
microtubules • Function:
• Support nuclear envelope • Cell-cell juntions (ie, those holding skin cells tightly
together)
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Microfilaments • Two intertwined strands of actin • Function
• Cell shape (cytoskeleton) • Muscle contraction
• Cell motility • Cell division
• Cytoplasmic streaming
Microtubule Operation
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Extensions of the Cell Membrane CILIA & FLAGELLA: • Hairlike projections that aid in cell movement • They are membrane-bound cylinders enclosing
a matrix area • The matrix consists of microtubules in a 9 + 2
pattern
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Centrioles • Short cylinders with a 9 + 0 pattern of microtubule
triplets • Help organize microtubules during animal cell division • Maybe involved with microtubule formation and in the
organization of cilia and flagella
Flagella • Sperm “tail”
• Motility (movement/swim)
Cilia • Hair-like
• Sweeping motion • Eg. In oviducts sweep ovum/zygote toward uterus • Eg. In Bronchi sweep up mucus coated debris, moving
it upward to be coughed or swallowed
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1. Nucleolus 2. Nucleus 3. Ribosome 4. Vesicle 5. Rough endoplasmic reticulum 6. Golgi apparatus (or "Golgi body") 7. Cytoskeleton 8. Smooth endoplasmic reticulum 9. Mitochondrion 10. Vacuole 11. Cytosol 12. Lysosome 13. Centriole
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