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					The Cell   Overview
           of cell
           function
           and
           structure
 The Cell: The Basic
     Unit of Life
The Cell is a highly complex and well
organized structure which manages
hundreds of thousand of complex reactions
almost every second.
The term Cell was first evoked by a biologist
called Robert Hooke in the 17 century, who
on observing a section of cork through a
microscope, noted that the plant stem was
divided into series of units or cells.
Cork Cell as viewed from a
microscope
The four characteristics of cells.

All organisms -living things-
are made of                              Cells do the
cells.                                   jobs that keep
                                         organisms

                      Cells              alive.




         Cells are the smallest
         part of a living thing.

                                These cells are like
                                tiny building blocks.
Cell Basics: All Organisms
     are Made of Cells
   The cell is the basic unit of structure & function
   The cell is the smallest unit that can still carry on all
    life processes
   Both unicellular (one celled) and Multicellular
    (many celled) organisms are composed of cells
   Before the 17th century, no one knew cells existed
   Most cells are too small to be seen with the
    unaided eye
   In the early 17th century microscopes were
    invented & cells were seen for the 1st time
  Cell Basics: Principles of
       the Cell Theory
 Allliving things are made of one or
  more cells
 Cells are the basic unit of
  structure & function in organisms
 Cells come only from the
  reproduction of existing cells
    Cell Basics: Cell Diversity
   Not all cells are alike
   Cells differ in size, shape, and function
   The female egg cell is the largest cell in
    the body & can be seen without a
    microscope
   Bacterial cells are some of the smallest
    cells & are only visible with a microscope
   Cells are limited in size by the ratio
    between their outer surface area & their
    volume
Cells come in a variety of shapes, & the shape which
helps determine the function of the cell (e.g. Nerve
cells are long to transmit messages in the body, while
red blood cells are disk shaped to move through blood
vessels)
     The Cell: Basic Unit of Life
 The cell is the         Cells can be divided
 smallest unit of life   into two principal
 capable of              types, prokaryotic
 independently           and Eukaryotic
 sustaining and          cells that is, with
 reproducing itself.     and without a
                         nucleus.

Cells are always building and breaking down
material. Cells release energy from foods, and
then use that energy to make needed cell parts.
A cells function is to make your body operate.
Prokaryotic vs. Eukaryotic
"Karyose" comes from a Greek word which
means "kernel," as in a kernel of grain. In
biology, we use this word root to refer to the
nucleus of a cell. "Pro" means "before," and
"eu" means "true," or "good." So
"Prokaryotic" means "before a nucleus," and
“Eukaryotic" means "possessing a true
nucleus." This is a big hint about one of the
differences between these two cell types.
Prokaryotic cells have no nuclei, while
Eukaryotic cells do have true nuclei.
nucleus       chloroplasts     Cell wall

          cytoplasm    Cell membrane
                cytoplasm
Cell membrane



                            Nucleus
   Animal Cells         Plant Cells
•Cell membrane     •Cell wall
•Cytoplasm         •Cell membrane
•Vacuoles          •Cytoplasm
•Nucleus           •Vacuoles
                   •Chloroplasts
                   •Nucleus

   Compare and Contrast plant
   and animal cells.
          Prokaryotic Cells
Prokaryotes were here first and for billions
  of years were the only form of life on Earth.

   Prokaryotic cells are less complex
   Unicellular (one celled)
   Do not have a nucleus & no membrane-
    bound organelles
   Most have a cell wall surrounding the cell
    membrane & a single, looped chromosome
    (genetic material) in the cytoplasm
          Prokaryotic Cells
   Prokaryotic cells feature three major
    shapes: rod shaped, spherical, and
    spiral.
   Prokaryotic cells include bacteria &
    blue-green bacteria.
   Prokaryotic cells are found only in the
    kingdom Monera
        Prokaryotic Cells
Prokaryotic Cells such as Bacteria perform many
important functions on earth. They serve as
decomposers, agents of fermentation, and play
an important role in our own digestive system.
Also, bacteria are involved in many nutrient
cycles such as the nitrogen cycle, which restores
nitrate into the soil for plants.
         Eukaryotic cells
   Eukaryotic cells have a true
    nucleus
   Animals, plants, fungi, and
    protists are eukaryotes
   Eukaryotic cells also contain
    membrane-bound organelles
    such as mitochondria and
    chloroplasts.
Eukaryotic
 cells
a.   Nucleus
b.   Chloroplast
c.   Golgi
d.   Mitochondria
Animal vs- Plant Cell




Animal Cell     Plant Cell
          Animal cell
An animal cell is a form of eukaryotic
cell which make up many tissues in
animals. The animal cell is distinct
from other eukaryotes, most notably
plant cells, as they lack cell walls and
chloroplasts, and they have smaller
vacuoles. Due to the lack of a rigid cell
wall, animal cells can adopt a variety
of shapes. Human cells are biologically
categorized as animal cells.
Animal cell
                Plant Cells
Plant cells are quite different from the cells of
  the other eukaryotic organisms. Their
  distinctive features are:
 A large central vacuole

 A cell wall made up of cellulose and protein

 They contain chlorophyll, the pigment that
  gives plants their green color and allows
  them to perform photosynthesis.
 Plant groups without flagella (including
  conifers and flowering plants) also lack
  centrioles that are present in animal cells.
Plant Cell
           Fungi Cells
Fungal cells are most similar to animal
  cells, with the following exceptions.
 A cell wall made of chitin.

 Only the most primitive fungi, chytrids,
  have flagella.
 Primitive fungi have no such divisions,
  and each organism is essentially a
  giant supercell. These fungi are
  described as coenocytic.
Fungi Cells
Cell structures we will cover
  Vacuole             Unit Membrane
  Chloroplast         Cell Membrane
  Ribosomes Nucleus
                      Cell Wall
  Golgi Apparatus
                      Chromatin-
  Mitochondrion
  Lysosome                Chromosomes

  Centriole
  Endoplasmic Reticulum
              Unit Membrane
                 Cell Membrane
   Separates the cytoplasm of the cell from its
    environment
   Protects the cell & controls what enters
    and leaves
   Cell membranes are selectively permeable
    only allowing certain materials to enter or
    leave
   The cell membrane is constantly breaking
    down & being reformed inside living cells.
   K. Certain small molecules such as CO2,
    H2O, & O2 can easily pass through them
    membrane
       Cell Membrane
Structure - same as unit membrane.

Function - acts as a boundary layer to
 contain the cytoplasm (fluid in cell)
           - interlocking surfaces bind
 cells together
           - selectively permeable to
 select chemicals that pass in and out of
 cells
               Cell Wall
Structure
    - a non-living secretion of the cell
  membrane, composed of cellulose
    - cellulose fibrils deposited in
  alternating layers for strength
    - contains pits (openings) that make it
  totally permeable
Function
    - provides protection from physical
  injury
    - together with vacuole, provides
  skeletal support
                  Nucleus
The nucleus (pl. nuclei; from Latin nucleus or
  nuculeus, kernel) is a membrane-enclosed
  organelle found in most eukaryotic cells.
 Contains most of the cell's genetic material, or
  DNA
Main structural elements of the nucleus are:
 nuclear envelope

 Nucleolus

 Chromatin

 nucleoplasm
              Nucleus
Nuclear Envelope
 Structure - two unit membranes
  with a fluid-filled space
       - nuclear pores present
       - outer membrane may be
  continuous with endoplasmic
  reticulum
 Function - selectively permeable to
  control movement in or out
            - contains nuclear contents
                 Nucleus
Nucleus - Is surrounded by a double
 membrane and contains the cell's DNA
 and the nucleolus, the site of RNA and
 ribosome production.

The nucleus regulates all cell activity. It
 does this by controlling the enzymes
 present.
             Nucleolus
Structure - non-membranous
  matrix of RNA (ribonucleic acid)
            and protein
Function - instructions in DNA are
  copied here
   - works with ribosome's in the
  synthesis of protein
 Chromatin-Chromosomes
 Chromatin    is a mass of
  uncoiled DNA and associated
  proteins called histones.
 When cell division begins,
  DNA coils around the proteins
  forming visible structures
  called chromosomes.
          Chromatin
Structure -composed of long thin
  strands of DNA

Function -contains instructions that
 control cell metabolism and
 heredity
    Chromosome Structure
       and Replication
 A chromatid is a single DNA
  molecule.
 Double-stranded chromosomes have
  two chromatids; normally, each one is
  identical to the other. The point where
  the two chromatids are attached is
  called the centromere.
     Endoplasmic Reticulum
Endoplasmic Reticulum (E.R.)
 Extensive internal membrane system
 throughout the cell which not only acts
 as a transport and communications
 system but also the principal site lipid
 synthesis and plays a role in protein
 synthesis.
    Endoplasmic Reticulum
            (ER)
   Endoplasmic Reticulum (ER) Structure -
    sheets of unit membrane with ribosomes
    on the outside
        - forms a tubular network throughout
    the cell

    Function - transports chemicals between
    cells and within cells
       - provides a large surface area for the
    organization of chemical reactions and
    synthesis
            Ribosome's

Ribosome Structure - non-
 membraneous, spherical bodies
 composed of
    RNA (ribonucleic acid) and
 protein enzymes

Function - site of protein synthesis
     Golgi Body or Apparatus
 Golgi Apparatus modifies,
  packages, & helps secrete cell
  products such as proteins and
  hormones
 Consists of a stack of flattened sacs
  called cisternae
 Receives products made by the ER
  or endoplasmic reticulum
           Mitochondria
Mitochondrion Structure - composed
 of modified double unit membrane
 (protein, lipid)
            - inner membrane infolded
 to form cristae
Function - site of cellular respiration
 i.e.. the release of chemical
              energy from food
Glucose + Oxygen ------> Carbon
 Dioxide + Water + Energy (ATP)
              Lysosome
Lysosome Structure - membrane bound
  bag containing hydrolytic enzymes
             - hydrolytic enzyme = (water
  split biological catalyst)
         i.e. using water to split chemical
  bonds
Function - break large molecules into small
  molecules by inserting a molecule of
  water into the chemical bond
             Vacuoles
Vacuole Structure
   - a single layer of unit membrane
 enclosing fluid in a sack
Vacuole Function
   - produces turgor pressure
 against cell wall for support
   - stores water and various
 chemicals
   - may store insoluble wastes
Vascular tissue transports food &
 water
              Chloroplast
Chloroplast Structure
    - composed of a double layer of modified
  membrane (protein,
      chlorophyll, lipid)
    - inner membrane invaginates to form layers
  called "grana"
      (sing., granum) where chlorophyll is
  concentrated
Function - site of photosynthesis

Chlorophyll
Carbon Dioxide + Water --------> Glucose + Oxygen
            radiant energy(light)      (food)
             Centriole

Centriole Structure - nine triplets of
 microtubules form one centriole
    - two centrioles form one
 centrosome

Function - forms spindle fibres to
 separate chromosomes during cell
            division
Cell Complexity

				
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