Cell Theory - Weeblybiology12-benabo.weebly.com/.../4/4/4/2/4442802/1.cells.pdf1 Cell Biology Cell...

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1 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

Transcript of Cell Theory - Weeblybiology12-benabo.weebly.com/.../4/4/4/2/4442802/1.cells.pdf1 Cell Biology Cell...

Page 1: Cell Theory - Weeblybiology12-benabo.weebly.com/.../4/4/4/2/4442802/1.cells.pdf1 Cell Biology Cell Theory & Cell Structures ! Cell Theory • refers to the idea that cells are the

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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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