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The cell is the structural and functional unit of all
 living organisms, sometimes called the
"building blocks of life.


•Unicellular organism
•Multicellular organism

Cell …Latin cella, a small room.
Coined by Robert Hooke …cork
cells and small rooms.




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 Cells are classified as prokaryotes or eukaryotes
      Representative organisms:
             eukaryotes-animals, plants, algae, protozoa, and
                          fungi.
             prokaryotes-bacteria (Eubacteria & Archaebacteria).




According to need for energy:
    Autotrophs -"self feeders".
    Heterotrophs -"other feeders"
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Some features distinguishing prokaryotic and
              eukaryotic cells
                     EUKARYOTES          PROKARYOTES

1. Nuclear body    •Bounded by a         •Not bounded by
                   nuclear membrane.     a nuclear
                                         membrane.
                   •Contains one or
                   more paired, linear   •Usually contains
                   chromosomes .         one circular
                                         chromosome.
                   •Nucleolus present.
                                         •No nucleolus.

2. Cell division   •By mitosis.          •Usually by
                                         binary fission.
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                    EUKARYOTES         PROKARYOTES

3. Cytoplasmic   • Fluid               •Fluid
membrane           phospholipid        phospholipid
                   bilayer.            bilayer usually
                                       lacking sterols.
                 • Capable of
                   endocytosis         •.Incapable of
                   (phagocytosis and   endocytosis and
                   pinocytosis) and    exocytosis.
                   exocytosis.
4. Cytoplasmic   • Ribosomes           •Ribosomes
structures         composed of a       composed of a 50S
                   60S and a 40S       and a 30S subunit
                   subunit forming     forming an 70S
                   an 80S              ribosome.
                   ribosome.                              6
                     EUKARYOTES            PROKARYOTES
                 •Chloroplasts serve       •No chloroplasts
                 for photosynthesis.       and mitotic
                 •Mitotic spindle- cell    spindeles.
                 division.
                 •microtubules, actin      • Internal
                 micofilaments, and        membrane-bound
                 intermediate              organelles are
                 filaments are             absent.
                 present.
5. Respiratory
                 •Located in              •Located in the
enzymes and
                 the                      cytoplasmic
electron
                 mitochondria.            membrane.
transport
chains

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                 EUKARYOTES         PROKARYOTES
6. Cell wall   • Usually            •Most
                 composed of        Eubacteria
                 cellulose or       have cell walls
                 chitin but         composed of
                 never              peptidoglycan.
                 containing
                 peptidoglycan.
               • Animal cells
                 and protozoans
                 lack cell walls
7. Locomotor   •May have            •Some have
organelles     flagella or cilia.   flagella
                                    •No cilia.
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      Structural Components of Cell:
The parts of the cell. Structure and function
      Cell membrane
           Its general structure
               Phospholipids
               Proteins
               Steroids
           Its function

       Nucleus nucleus
                Its structure
                       nucleolus
                Its function

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The cytoplasm
   Protein producing orangelles
       The endoplastic reticulum
       Ribosomes
       The golgi apparatus
       Lysosomes

    Energy use and production
       Chloroplasts
       Mitochondria

    Specialty structures
       Centrioles
       Vacuoles
       Cell walls
       Cilia and flagella
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                  Cell membrane



• It is only 7.5 nm thick.
•The thin nearly invisible
structure that surrounds the
cytoplasm of the cell
•It is a highly selective filter
that maintains the unequal
concentration of ions on
either side.




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        phospholipids                   proteins




                                               steroids




 Phospholipids are the round yellow structures with the blue
tails, the proteins are the lumpy structures that are scattered
around among the phospholipids.
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•    Contains few type of lipid molecules but many kinds
     of proteins
•    Protein type
a.   Receptor protein
b.   Integral protein
c.   Enzymes




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  Properties of the lipid bilayer
• Structure
• Asymmetry
     Phospholipid asymmetry
     Carbohydrate asymmetry
     Protien asymmetry
• Fluidity
• Mobility
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                      Diffusion
• Molecule moving naturally into the cell
through diffusion drags another molecule into
the cell. (glucose hitches a ride with sodium).
• Some proteins actively use energy from the
ATPs (sodium/potassium pump )




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Carrier Proteins

• Move specific molecules through the
membrane one at a time.



 Channel proteins
 • Channel proteins extend
 through the bilipid layer.
 • They form a pore through
 the membrane that can move
 molecules in several ways.


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Marker proteins

•Serve to identify the cell.
• The immune system uses these
proteins to tell friendly cells from
foreign invaders



 Receptor Proteins

• These proteins are used in
intercellular communication



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                Endocytosis
• Engulfs structures much too large to fit through the
pores
•3 forms pinocytosis, phagocytosis, receptor mediated
endocytosis




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                Exocytosis


     Release of large molecules from the cell.
Nerve cells release the neurotransmitter chemicals




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                  Cytoplasm
•Everything between the cell membrane and the nuclear
envelope.
•Consists of primarily of water.
•Contains organelles ,salts, dissolved gasses and
nutrients.
3 categories of organellae

Group1
Those involved in protein production
Group 2
Those involved in energy
production
Group 3
Speciality organelle
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         Protein Producing Organelles - Ribosome




•The rough E.R. has ribosomes attached to it.
•They manufacture proteins for the cell.

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Protein Producing Organelles- Endoplastic Reticulum
 •A folded system of membranes that loop back and
 forth.
 •This membrane provides a surface area for cell
 reactions.
 •Site of lipid production.

     Smooth E.R.                    Rough E.R




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               Protein Producing Organelles - The Golgi
the cytoplasm.
               Apparatus




   • Packaging proteins .
   •Proteins sack like cisternae     squeezed off into
   cytoplasm.
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    Protein Producing Organelles - Lysosomes




• “Suicide sacks”,produced by the golgi body.
•Consist of a single membrane surrounding powerful
digestive enzymes.
•Uncontrolled release of lysosome contents into the
cytoplasm is also a component of necrotic cell death.
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The path of lysosomes:




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• Peroxisomes
• Responsible for protecting the cell from its own
  production of toxic hydrogen peroxide.
• White blood cells produce hydrogen peroxide to kill
  bacteria. The oxidative enzymes in peroxisomes break
  down the hydrogen peroxide into water and oxygen.


• Secretory Vesicles
• Cell secretions - e.g. hormones, neurotransmitters are
  packaged in secretory vesicles at the Golgi apparatus.
• The secretory vesicles are then transported to the cell
  surface for release


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             Energy Producing Organelles -
                      Mitochondrion




The Mitochondrion




   •Site of aerobic respiration.
   •Most of the key processes of aerobic respiration occur
   across its inner membrane.
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Structure of mitochondria:




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                Nucleus-nuclear envelop &
                      nucleolus




• The nuclear envelope is a double membrane.
• Has large pores through which materials pass back and
forth
• The nucleus is the headquarters of the cell.
• It regulates all cell activity.                   40
Nucleolus




•Within the nucleus are found chromatin and a structure
called the nucleolus.
•The nucleolus is a knot of chromatin.
•During the period between cell divisions, when the
chromosomes are in their extended state, 1 or more of them
(10 in human cells) have loops extending into a spherical
mass called the nucleolus.
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 Nuclear pore
 complex:
•Perforated with thousands of
pores.
•Each is constructed from a
number different proteins
called nucleoporins.
•25 nm wide.
•Transport through the
nuclear pore complexes is
active.
•Import-proteins from cytosol.
•Export-RNAs & transcription
proteins.                        42
•Chromosomes are long threads of material called chromatin.
• This material is composed of a central core of DNA (making up
about 40% of the chromosome), and packaging proteins (about
60%).
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•DNA contains the information for the production of
proteins.
•This information is encoded in the 4 DNA bases. Adenine,
thymine, cytocine, and guanine.
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                Centrosome




Also called the "microtubule organizing center", is an
                       area in
       the cell where microtubles are produced




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• During animal cell division, the centrosome divides
  and the centrioles replicate . The result is two
  centrosomes, each with its own pair of centrioles.
  The two centrosomes move to opposite ends of the
  nucleus,
• and from each centrosome, microtubules grow into
  a "spindle" which
• is responsible for separating replicated
  chromosomes into the two daughter cells.




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 Speciality structures-
      Centrioles

•Found only in animal cells.
•Function in cell division.
•Protein fibers in sets of 3 are
arranged in 9 groups.


Speciality structures
       Vacuoles
• Large empty appearing areas found in
the cytoplasm.
•Usually found in plant cells where they
store waste..
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      Cytoskeleton
• Microtubules
• Intermediate filaments
• Microfilaments


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                 Microtubules and
                  Microfilaments


•These are hair like extensions off of the
cell membrane.
•In unicellular organisms their job is
locomotion .
• In large multicell organisms they move
fluid past the cell.




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              Cilia & flagella

• Consist of microtubules
• Motile extensions
• Cilia are abundant on free surface of some
  epithelial cells
• To & fro movement
• Cells usually have only one flagella which is
  larger than cilia
• Seen as tail of sperm cell




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      INTERCELLULAR JUNCTIONS

1.  Occluding (tight) junctions (Zonula Occludence).
2.  Adhesive junctions
    Cell-to-Cell.
     • Zonula adherence.
     • Macula adherence (desmosomes).
    Cell-to-matrix.
     • Focal adhesions.
     • Hemidesmosomes.
3. Communicating (gap) junctions.

“Cell-cell and cell-matrix junctions have important
roles in the differentiation, development, and function
of normal cells, tissues, and organs.”                  54
On the molecular level, intercellular junctions
    typically consist of three components
•   Trance membrane adhesive protein (TMP).
•   Cytoplasmic adapter protein (CAP) and
•   Cytoskeletal filament (CF).

These three components differ depending on the type
   of junction.




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Tight junction

TMP-
-Occludin.
-Junctional adhesion
molecule.
CAP-
-Cell polarity related
protein.
-Vesicular transport
related      proteins.
-Tumor suppressor protein.
-Transcription factor.       56
   Desmosome


•The     interaction   of
transmembrane
proteins of two adjacent
cells results in a dense
line in the middle of the
intercellular space at
the desmosomes.




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Hemidesmosomes




Junctional epithelium   Hemidesmosomes
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  Gap junctions
•These are spot like
jnunctions b/t two opposing
cells.
•Maintain a gap about 2-
3nm.
•TMP-connexin family.
•6 connexin molecules
form into a connexon
molecule.
•Aqueous channels run
through the TMPs-ions
and signalling molecules
move from one cell to
adjacent cell.                59
Cell Cycle:
Cells go through two basic phases: Mitosis, Interphase.




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Mitosis   is nuclear division plus cytokinesis, and produces
          two identical daughter cells.


   Prophase
   Prometaphase
   Metaphase
   Anaphase
   Telophase
   Cytokinesis




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Meiosis
 •Formation of gametes – second type of division.
 •Responsible for production of haploid reproductive
 cells.
 •This process consists of two successive nuclear
 divisions without an intervening period of DNA
 replication.




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Comparing Meiosis and Mitosis:

 •Chromosome behavior
    1.Mitosis: Homologous chromosomes
    independent
    2.Meiosis: Homologous chromosomes pair
 • Chromosome number- reduction in meiosis
    1.Mitosis- identical daughter cells
    2.Meiosis- daughter cells haploid
 •Genetic identity of progeny:
    1.Mitosis: identical daughter cells.
    2.Meiosis: daughter cells have new
    assortment of parental chromosomes.
    3.Meiosis: chromatids not identical,
    crossing over.
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Mitosis




Meiosis




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                      Apoptosis
                    Programmed cell death

• Form of cell death and is an active process.
• Enzyme cuts up DNA not protected by histones
• Cell contents are packaged up and destroyed by large
  scavenger cells
• In contrast necrosis is a passive response to severe injury
• Unlike apoptosis, necrosis is not a neat disposal process,
  but causes great inflammation




  neutrophil                zieosis         Apoptic bodies
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     The
   Protein
  secretion
     and
transcription
      of
    DNA

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Transcription:




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Translation




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      Etiology of Cell Injury
• Genetic causes
• Acquired causes
1. Hypoxia and ischaemia
2. Physical agents
3. Chemicals and drugs
4. Microbial agents
5. Immunologic agents
6. Nutritional derangements
7. Psychologic factors          71
Pathogenesis of cell injury




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Free radical mediated cell injury




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Pathogenesis
 of physical
    injury


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     Morphology of cell injury
Morphology of reversible cell injury
• Cellular swelling
• Hyaline change
      Intracellular hyaline
      Extracellular hyaline
• Mucoid change
      Epithelial mucin
      Connective tissue mucin
• Heat shock protiens and ubiquitin    77
Morphology of irreversible cell injury

 •   Autolysis
 •   Necrosis
 •   Apoptosis
 •   Gangrene
 •   Pathologic calcifications

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         Cellular Adaptations
•   Atrophy
•   Hypertrophy
•   Hyperplasia
•   Metaplasia
•   Dysplasia

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Gray's Anatomy – 39th Edition, Churchill
Eivingstone.
Hole’s Human Anatomy and Physiology-10th edition
Tencate’s Oral Histology-10th edi.
Text/Atlas of HISTOLOGY – Leeson, Leeson,
Paparo..
Orban’s Oral histology & Embryology-S.N.
Bhaskar,11th edi.
Textbook of Pathology– Harsh Mohan -5thedi.
www.cellsalive.com
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