Cell Structure and Function

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Cell Structure and Function
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CELL STRUCTURE AND FUNCTION

• 1. WHAT IS THE CELL THEORY?
• 2. WHAT IS THE STRUCTURE OF A PROKARYOTIC CELL?
• 3. WHAT IS THE STRUCTURE AND FUNCTION OF
  EUKARYOTIC CELLS?
• 4. WHERE DID EUKARYOTIC CELLS COME FROM?

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Cell Theory

• Cell theory states all organisms are composed of
  cells, that cells are the structural and
  functional units of life and come only from
  preexisting cells.
• One of unifying concepts of biology.

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CELL KNOWLEDGE

• ABOUT 350 B.C. ARISTOTLE SAID ALL THINGS ARE
  COMPOSED OF 4 ELEMENTS AIR, WATER, EARTH, FIRE
• 1600S MICROSCOPE
• 1680S
• ROBERT HOOKE THE CELL
• ANTON VON LEEUWENHOEK-FATHER OF CELL BIOLOGY

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• MID 1800S
• SCHLEIDEN- BOTANIST
• SCHWANN- ZOOLOGIST
• CELLS ARE THE STRUCTUAL AND FUNCTIONAL UNITS OF
  LIFE
• LATE 1800S
• VIRCHOW
• CELLS COME FROM PREEXISTING CELLS

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Fig. 4B
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CELL THEORY

• 1. CELLS ARE THE STRUCTURAL UNITS OF LIFE
• 2. CELLS ARE THE FUNCTIONAL UNITS OF LIFE
• 3. CELLS COME FROM CELLS

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Cell Size

• Most cells are much smaller than one millimeter.
• Some as small as one micrometer.
• Small cells are likely to have an adequate
  surface area for exchanging wastes for nutrients.
• Cells that specialize in absorption have
  modifications that greatly increase the surface
  area per volume of the cell.

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Organism Sizes
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CELL SURFACE TO VOLUME RATIO

• A CUBE 1mm TALL HAS A SURFACE
• AREA OF 1mm X 1mm X6 SIDES 6 Sq.mm AND A
  VOLUME OF 1mm X 1mm X1mm 1 CUBIC mm
• THE SURFACE TO VOLUME RATIO IS 61

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CELL SURFACE TO VOLUME RATIO

• A CUBE 2mm TALL HAS A SURFACE
• AREA OF 2mm X 2mm X6 SIDES 24 Sq.mm AND A
  VOLUME OF 2mm X 2mm X2mm 8 CUBIC mm
• THE SURFACE TO VOLUME RATIO IS 31

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Prokaryotic Cells

• Lack a membrane-bounded nucleus.
• Structurally simple.
• Can be divided into two domains
• Bacteria
• Three Shapes
• Bacillus (rod)
• Coccus (spherical)
• Spirilla (spiral)
• Archaea
• Live in extreme habitats.

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Prokaryotic Cells
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Prokaryotic Cells

• Cell Envelopes
• Includes plasma membrane, cell wall, and
  glycocalyx (layer of polysaccharides outside cell
  wall).
• Capsule Well-organized layer.
• Form internal pouches (mesosomes).

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Prokaryotic Cells

• Cytoplasm
• Cytoplasm is a semifluid solution encapsulated by
  plasma membrane.
• Inclusion Bodies - Stored granules of various
  substances.
• Appendages
• Flagella
• Fimbriae
• Sex Pili

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Eukaryotic Cells

• Members of domain Eukarya.
• Contain membrane-bounded nucleus.
• Contain specialized organelles.
• Contain plasma membrane.

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Organelles

• Organelles of endomembrane system communicate
  with one another.
• Basically self-sufficient
• Compartmentalization allows eukaryotic cells to
  be larger than prokaryotic cells.

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Animal Cell Anatomy
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Plant Cell Anatomy
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Nucleus

• Contains chromatin in semifluid nucleoplasm.
• Condense to form chromosomes.
• Separated from cytoplasm by double-membrane
  nuclear envelope.
• Nuclear pores permit passage in and out of the
  nucleus.

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Anatomy of Nucleus
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Ribosomes

• Composed of large and small subunits that serve
  in protein synthesis.
• Subunits made in nucleolus.
• Occur singly and in groups, and may become
  attached to endoplasmic reticulum.

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Endomembrane System

• Consists of nuclear envelope, membranes of
  endoplasmic reticulum, Golgi apparatus, and
  several types of vesicles.
• Restrict enzymatic reactions to specific
  compartments within cell.
• Endoplasmic Reticulum
• Rough - Studded with ribosomes.
• Smooth - No ribosomes.

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Endoplasmic Reticulum
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Endomembrane System

• Golgi Apparatus
• Consists of flattened, curved saccules.
• Modifies proteins and lipids and packages them in
  vesicles.

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Endomembrane System

• Lysosomes
• Membrane-bounded vesicles produced by the Golgi
  apparatus.
• Engage in digestion of molecules and apoptosis
  (programmed cell death).

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Peroxisomes and Vacuoles

• Peroxisomes are membrane-bounded vesicles that
  enclose enzymes.
• Enzymes are cell-specific
• Vacuoles are membranous sacs that are larger than
  vesicles.
• Store substances
• Plants cells typically have a central vacuole
  that functions in storage of nutrients and waste
  products.

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Energy-Related Organelles

• Chloroplasts use solar energy to synthesize
  carbohydrates.
• Photosynthesis
• Chloroplasts are green due to the green pigment
  chlorophyll.
• Stroma
• Granum

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Chloroplast Structure
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Energy-Related Organelles

• Mitochondria are involved in cellular
  respiration.
• Produce most of ATP utilized by the cell.
• Cristae - Inner membrane that encloses matrix.
• Matrix - Enzymes that break down nutrient
  molecules.

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Mitochondrion Structure
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Cytoskeleton

• Cytoskeleton serves as internal skeleton that
  maintains cell shape and assists in movement of
  its parts.
• Actin Filaments
• Pseudopods
• Intermediate Filaments
• Microtubules

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Centrioles, Cilia, and Flagella

• Centrioles are short cylinders with a 9 0
  pattern of microtubule triplets that may give
  rise to basal bodies of cilia and flagella.
• Cilia and flagella are hairlike projections with
  a 9 2 pattern of microtubules that aid in cell
  movement.
• In eukaryotes, cilia are much shorter than
  flagella.

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EXTRA CREDIT CHART

• CELL STRUCTURES
• __________________________________________________
  __________________________________________________
  ___________________NAME COMPOSITION
  SKETCH LOCATION FUNCTION PROKAYOTE/EUKARYOTE
  (PLANT/ANIMAL)
• __________________________________________________
  __________________________________________________
  __________________
• 1.PLASMA MEMBRANE
• 2. NUCLEUS
• 3 NUCLEAR MEMBRANE
• 4. CHROMOSOMES (DNA)
• 5. LYSOSOMES
• 6. CENTRIOLES
• 7. CELL WALL
• 8. MITOCHONDRIA
• 9. ENDOPLASMIC RETICULUM (ROUGH SMOOTH)
• 10. RIBOSOME
• 11. GOLGI APPARATUS
• 12. VACUOLE/VESICLE
• 13 PEROXISOME
• 14. CYTOSKELETON
• 15. CILIA/FLAGELLA

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Table 4.1
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WHERE DID EUKARYOTIC CELLS COME FROM?

• Accoring to the endosymbiotic hypothesis,
  mitochondria and chloroplasts were once
  free-living bacteria. A nucleated cell took in
  an aerobic bacteria which became its
  mitochondria. A nucleated cell with mitochondra
  took in a photosynthetic bacteria which became
  its chloroplasts

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REVIEW

• KNOW THE CELL STRUCTURES AND FUNCTIONS FOR
  PROKARYOTES AND EUKARYOTES
• WHAT ARE THE 3 PARTS OF THE CELL THEORY
• WHY ARE CELLS VERY SMALL. USE THE COMPARISON OF
  A 6mm CUBE AND A 12mm CUBE

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