Chapter 6

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Chapter 6 A Tour of the Cell
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Review Metric System

• What is a µm?
• What is a mm?
• How many µm is 22 mm?

10-6 m
10-3 m
2,200 µm or 2.2 x 103 µm
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Size Range of Cells

• Most cells are in the range of 1 to 100 µm
• Not visible with unaided eyes
• Light microscopes are capable of resolving most
  plant, animal, and bacterial cells
• Electron microscopes are used for smaller cells
  and molecules

Figure 6.2
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1. Light Microscope
- First used by Renaissance scientists (Remember
Hooke and Von Leeuwenhoek). - Visible light is
passed through a specimen and then through
multiple lenses to enlarge the apparent
object. - Object is usually stained so that
some light is absorbed or induced to fluoresce.
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• Electron microscopes
• - Invented in the 1950s
• - Beam of electrons is focused through or onto
  the surface of a specimen
• - Transmission electron microscope (TEM)
  internal cell structure
• - Scanning electron microscope (SEM) surface
  of specimen
•  
• Figure 6.4 (p. 96) Electron micrographs.
  Views are of cilia in the windpipe of a rabbit.

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TEM vs. SEM
Figure 6.4

• Transmission electron microscopes (TEM) are used
  mainly to study the internal structure of cells

• Scanning electron microscopes (SEM) are used to
  study the surface of cells

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As noted in Chapter 1, one of the Eleven Unifying
Themes of Biology is that the Cell is the basic
Unit of Life. Remember that there are two
types of Cells   Prokaryotic and
Eukaryotic Prokaryotic cells do not have a
membrane enclosed nucleus or organelles. What
are the two types of Prokaryotes?
Bacteria and Archae
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Figure 6.6 (p. 98) A prokaryotic cell. From
Fig. 6.6, remember these different
components   a. Nucleoid location of DNA,
not enclosed by a membrane in contrast to
eukaryotic cells. b. Pili Structures most
often used for attachment to soil, tissue, etc.,
can be toxic to higher organisms. c. Ribosomes
Organelles that synthesize protein. d. Cell
Wall Rigid structure that maintains cells
shape protects it from rupture. e. Capsule
Slime-like layer used for protection and
attachment. f. Flagellum (-a, pl.) Used for
locomotion by a cork-screw motion. g. Plasma
Membrane Controls what comes in and out of
cell site of most energy production.
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Prokaryotic Cell
Figure 6.6
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2. Eukaryotic cells contain a nucleus and
organelles that are sub-cellular structures that
perform specialized functions within the cell.
Know the following from  Figure 6.9 (p. 100)
Overview of an animal cell. Figure 6.9 (p. 101)
Overview of a plant cell.   a. Nucleus
contains majority of the genes in the eukaryotic
cell present in the cells chromosomes.   b.
Cytoplasm region between the nucleus and plasma
membrane organelles are suspended in this region
  c. Plasma Membrane barrier that allows
exchange of oxygen, nutrients, and waste into and
out of the cell   d. Cell Wall maintains
shape and structure of cell (found only in plant
cells)  
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Animal Cell
Figure 6.9
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e. Ribosomes carry out protein synthesis  f.
Endoplasmic Reticulum (ER) site of membrane
synthesis and some metabolic processes. There
are two types of ER - Rough ER covered with
ribosomes (synthesis of proteins) - Smooth
ER surface lacks ribosomes g. Golgi
Apparatus modifies, stores, and secretes
products of ER h. Lysosomes bodies of enzymes
that are used to digest macromolecules (found
only in animal cells) and harmful compounds  
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i. Vacuoles membrane-bounded sacs within
cells - Food vacuoles store and digest
food - Contractile vacuoles excrete excess
water - Central vacuole storage of excess
organic and inorganic compounds isolation j.
Mitochondria cellular respiration occurs and
ATP is generated   k. Chloroplasts
photosynthesis ? convert light energy to chemical
energy (found only in plant cells)
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Animal Cell
Figure 6.9
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Plant Cell
Figure 7.8
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• Further details and Figures
•  
• The Nucleus (pp. 102 and 103) Note the double
  membrane and the chromatin (cellular DNA plus
  protein coat) in Fig. 6.10.
• 2. Endomembrane System (pp 104 - 109). Functions
  to compartmentalize cellular activities.
  Includes the nuclear envelope, endoplasmic
  reticulum, Golgi apparatus, lysosomes, vacuoles,
  and the plasma membrane.

In the film accompanying this section, note where
a secretory protein is produced (endoplasmic
reticulum, rough), how the protein moves to the
Golgi apparatus (transported in a vesicle), that
the protein is modified by the Golgi apparatus,
and then transported to the plasma membrane where
it is released to the outside of the
cell.   Note secretory proteins are secreted
to the outside of the cell so that they can
perform functions outside the cell. Can you
think of any?
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Fig. 6.12
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3. Mitochondria and Chloroplasts

• Mitochondrion - site of respiration(production
  of energy from fats, sugars and other organic
  molecules resulting in carbon dioxide, water and
  waste

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Chloroplasts - Site of photosynthesis (production
of sugars and energy from carbon dioxide, water
and light
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4. Cytoskeleton Network of fibers that extend
throughout the cytoplasm. Aids the cell in
maintaining its shape. Especially true for
animal cells that do not have cell walls, as
plants cells do. Note Fig. 6.20 and Table 6.1.
Remember the following two cytoskeleton
components and their functions   Microtublues
subset of these responsible for the beating of
cilia and flagella in eukarytoic cells. Note
Figs. 6.23 and 6.24.   Microfilaments subset of
these is responsible for the contraction of
muscle cells. Note Fig. 6.27.
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