Cell Theory

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Cell Theory
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UNIT II - CELL STUFF

• Chapter 4 Cells
• Chapter 5 Cellular Architecture
• Chapter 15 DNA structure and replication
• Chapter 16 Gene Function (Protein Synthesis)

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Cell Theory/Microscopy

• Two men from the 1600s Hooke
• Leeuwenhoek
• From the 1800s
• Schleiden
• Schwann

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Microscopy Leeuwenhoek

• Dutch scientist interested in lens grinding
• Produced wonderful microscopes
• pond water, tooth scum and semen

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Leeuwenhoek

• Told others of his finds and drew detailed
  drawings
• Microbiology

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Microscopy Robert Hooke

• English scientist
• Also built a microscope
• He actually invented the term cell because it
  reminded him of the cells in a honeycomb.

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HOOKES VIEW OF WINE CORK SLICED THINLY
CELLS
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Cell Theory Schleiden and Schwann

• German scientists helped to establish the Cell
  Theory
• Schleiden - a botanist - studied plants
• Schwann - a zoologist - studied animals

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• In the 1830s they stated jointly that
• ALL LIVING THINGS ARE COMPOSED OF CELLS

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More Cell Theory

• In the 1850s people accepted the cell theory but
  wondered -
• Where did cells come from in the first place?
• Spontaneous generation was one answer ...

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Spontaneous Generation

• More troublesome were the bacteria and fungi
  found in nature
• Many people believed these could form
  spontaneously
• Not Pasteur and Virchow though

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Louis Pasteur

• French scientist
• Cooked broth very thoroughly and sealed it
• Nothing grew in this broth - Pasteurization was
  invented
• Rivals said lack of Oxygen kept life from
  developing

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Pasteurs Revenge

• Pasteur proved them wrong however with a simple
  experiment

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Virchow

• similar experiments
• same conclusions
• Living cells come from previously existing cells
• There is no spontaneous generation

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Modern Cell Theory

• All organisms composed of one or more cells
• Cells are smallest living things-basic unit of
  organization of life
• Cells arise only from pre-existing cells

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Cell Types ProkaryoticEukaryoticArchaea
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Types of Cells

• Biologists today recognize two basic types of
  cells
• PROKARYOTIC
• EUKARYOTIC
• Archaea (Newly recognized cell type)

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Prokaryotic Cells

• Very simple, primitive
• No internal compartments
• No nucleus
• Very small
• Bacteria

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Eukaryotic Cells

• Complex internal structure
• Compartmentalization of chemistry
• Nucleus
• Varying sizes
• Typical plant and animal cells

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Archeae cells

• Newly recognized
• Similar to prokaryotes
• DNA similar to eukaryotes
• Unusual
• Different

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Overview of Cell Structure

• Surrounded by Plasma Membrane
• Genetic Material in central region
• Cytoplasm

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Cell Membrane
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Cell Membranes

• Cell membranes are composed of phospholipids
  mostly
• Some proteins and pores are also found
• The phospholipids are good barriers to hold in or
  hold out materials

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Membrane Proteins

• Transport channel
• Enzyme
• Cell Surface Receptor/Marker
• Attachment of cytoskeleton

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Functions of Cell Membrane

• Passage of water (in/out)
• Passage of bulk material
• Selective transport of substances

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Functions of Cell Membrane

• Reception of information
• Expression of cell identity
• Physical connection with other cells

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Prokaryotic Cell Structure
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Prokaryotic Cells

• Prokaryotic cells have
• no membrane enclosure around DNA
• small size (1/10th to 1/100th of normal)
• few organelles
• The word prokaryotic means primitive or simple
  nucleus
• Pro (before) karyon (kernel)

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Prokaryotic Cell Diagram
This prokaryotic cell shows many of the commonly
observed prokaryotic structures
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No membrane-bound nucleus!
single, circular molecule of DNA contains the
coded instructions to operate and reproduce the
cell
Ribosomes
Ribosomes are small organelles composed of RNA
used for the process of translation or protein
synthesis .
Inclusions
Inclusions are local accumulations of food, waste
or other materials.
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Prokaryotic Cell
Locomotion Protein Flagellin Spins
Jelly-like coat Protection

• Notice the capsule and flagellum

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Eukaryotic Cell Structure
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EUKARYOTIC CELLS

• Familiar plant, animal, fungal and protista cells
  
• Much larger than bacterial cells and more complex
• Complex structure of the cytoplasm

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Some Common Shapes of Human Cells
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Some Common Shapes of Human
Cells
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Eukaryotic Membranes

• Eukaryotic cell membranes are basically same
  structure as prokaryotic membranes
• SURROUND THE CELL
• FORM OR SURROUND MANY CELL ORGANELLES

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Membrane-bound organelles

• NUCLEUS
• ENDOPLASMIC RETICULUM
• GOLGI BODIES
• VACUOLES AND VESSICLES
• LYSOSOMES
• MITROCHONDRIA

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NUCLEUS

• DNA
• Chromatin
• Chromosomes
• Nucleolus
• rRNA synthesis
• Ribosome assembly
• Nucleoplasm
• Pores

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ENDOPLASMIC RETICULUM

• Network of membrane tubules in the cytoplasm
• Increases the surface area to volume ratio
• Eukaryotic cells are much bigger and need more
  surface area to exchange materials

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Has attached Ribosomes and is involved in
Protein synthesis
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Smooth ER has no ribosomes - lipids and
carbohydrates are built here
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Golgi Apparatus (Bodies)

• Continuous with ER
• Highly folded ER tubes make up the Golgi Bodies
  of cells
• The folds are called cisternae
• Golgi Bodies are the processing centers of cells
  - the loading docks

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GOLGI BODIES (continued)

• Collect, package,modify molecules synthesized at
  one location, used at another
• Larger vacuoles and smaller vesicles contain
  packaged molecules
• These may be enzymes, hormones, proteins, lipids,
  etc.

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VACUOLES

• Large membrane packages
• Contain solids, liquids
• Large Central Vacuole in plants
• Contains water
• Concentrated storage materials
• Starch -Sulfur -Oil

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LYSOSOMES

• Specialized vacuoles
• Filled with hydrolytic enzymes
• Digestive enzymes capable of hydrolysis
• Cellular Garbage men
• clean up old, worn-out organelles
• areas of damage
• digest phagocytized material

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MITOCHONDRIA

• Powerhouses of cells
• ATP synthesis occurs within mitochondria
• Double membrane structures with internal CRISTAE
  or folds of the inner membrane
• Matrix inside inner membrane
• Contain own DNA

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NON-MEMBRANE BOUND ORGANELLES

• Ribosomes
• Microtubules and Microfilaments
• Centrioles
• Cilia and Flagella

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RIBOSOMES

• Composed of RNA and Protein
• 2 subunits 1 large, 1 small
• Manufacture of protein
• Often on Endoplasmic reticulum
• Also free in cytoplasm

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Ribosomes attach to mRNA during protein synthesis
Ribosomes
Protein being built
mRNA
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CYTOSKELETONMICROTUBULES MICROFILAMENTS

• Hollow tube of TUBULIN protein
• Structural support
• Movement

• Fiberlike structures
• ACTIN Protein
• Cell contraction
• Cell framework

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CENTRIOLES

• 2 sets of microtubules at right angles to each
  other
• 9 groups of microtubules in each set
• animal cells
• cell division
• assembly and organization of microtubules

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CILIA AND FLAGELLA

• Flagella long and few
• Cilia Short and many
• 9 pairs microtubules
• PLUS 2 more in center
• 9 2 arrangement
• Covered with cell membrane material

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PLANT CELLS

• JUST THE DIFFERENCES IF YOU DONT MIND !!!!

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HOW DO PLANT CELLSDIFFER?

• Cellulose cell wall
• Large central vacuole
• Higher plants do NOT have centrioles (mosses -
  flowers)
• Have plastids in their cells

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CELLULOSE CELL WALLS
Help with support of the plant cells and the
plant itself
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CENTRAL VACUOLE
Most of the internal space in a plant cell is
occupied by the central vacuole
The central vacuole creates an outward push
called turgor or turgor pressure which helps
support the plant cell. A wilted plant has
lost turgor.
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Cell Membrane
CELL 1
CELL 2
PLASMODESMATA
Communication
Cell Wall
Space - MIDDLE LAMELLA - filled by PECTINS
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While were talking about cellular connections

• Plants plasmodesmata
• Plants Adhesion of cells
• Middle lamella
• Animals Gap junctions
• heart muscle cells example
• Animals Adhesion of cells
• Tight Junctions intestinal lining
• Desmososmes skin

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CENTRIOLES

• Higher plant cells do NOT have centrioles
• -mosses, ferns, etc.
• Still make spindle fibers and exhibit normal cell
  division

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PLASTIDS

• Plastids may be one of three types
• CHLOROPLASTS - GREEN PLASTIDS
• LEUCOPLASTS - WHITE PLASTIDS
• CHROMOPLASTS -OTHER COLORS

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CHLOROPLASTS
Chloroplasts have a double membrane
like mitochondria
STROMA is the space between the grana
GRANA are the folds of the inner membrane
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CHLOROPLASTS
Light
Sugar
Chloroplasts are the sites of photosynthesis withi
n plant cells.
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OTHER PLASTIDS

• Leucoplasts starch-storing plastids
• plant organs like potatoes
• Chromoplasts pigment storing plastids
• colored plant organs like tomatoes , banana
  peels , flowers, or fall leaves