Transcript Anatomy of the Eukaryotic Cell

Anatomy of the Eukaryotic Cell
This lecture will be a brief review of eukaryotic
structure and function. It is important that you
have a clear understanding of these concepts so
that you can move on to prokaryotic cellular
structure and function.
Structures external to cell wall
• Some eukaryotic cells have appendages for motility.
Motility is important for the organism to acquire nutrients
and get away from toxic or harmful things in the
environment.
• Flagella on eukaryotic cells are few in number (1 or ) and
long.
– Flagellar movement is wavelike, like cracking a whip.
• Cilia are also used for motility.
– They are more numerous and much shorter than flagella (resemble
hairs). They work like oars on a boat for move the cell from place
to place.
– Fewer types of cells have cilia as compared to those that have
flagella.
Structures External to Cell Wall
Continued
• Glycocalyx: outermost covering found on most cells.
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The glycocalyx is usually composed of sugars.
It functions to strengthen the cell surface.
It aids in adherence to other cells and surfaces.
It is important in signal reception between cells and the
environment.
– Generally the glycocalyx is categorized as either a capsule or a
slime layer.
– Ex. The glycocalyx is like the sugar coating on a jawbreaker.
Underneath that first colored sugar coating there are many other
layers.
Cell Wall
• Not all eukaryotes have a cell wall.
• Plants and most algae have a cell wall composed
of cellulose. Other cell walls are composed of
pectin, mannans and minerals.
• Fungi have cell walls composed of chitin.
– Chitin is the same component that makes up the
exoskeleton of crustaceans and insects.
• The cell wall provides structure and shape to the
cell. For example, plant cells look rectangular. It
is the cell wall that holds the cell in that particular
shape.
Cell/Plasma Membrane
aka. Cytoplasmic Membrane
• The cell membrane is a phospholipid bilayer. That means
that each half of the membrane is composed of a phosphate
group with 2 lipid chains attached to it. (See diagram on
next page.) You can also find a diagram of a phophate
group on page 44 of your textbook.
• Within the lipid bilayer there are proteins. These proteins
are often used to transport nutrients into the cell and waste
outside of the cell.
• The cell membrane also acts as a selectively permeable
barrier for the transport of nutrients into and out of the cell.
• In addition it encloses the cell’s organelles.
Outside Cell
Phosphate Group
Lipid or fat chain
*Important! *
Transport protein
within cell membrane
R
O
O
Phosphate group looks like this
P
O
R
O
-
The phosphorus
loves the protons
from the oxygen. It
pulls the protons
towards it and leaves
the electrons on the
outer edge of the
oxygen. This
creates a slight
negative charge on
the phosphate
group. Ultimately
the cell membrane is
negatively charged.
Inside Cell
Structures inside cell membrane
• The cell membrane encloses the cytoplasm. The
cytoplasm is composed of a large amount of water.
It is a substance in which various cellular
components are found.
– It contains the cell’s organelles.
– It contains microfilaments, a network of protein strands
used by phagocytes to form pseudopods.
– It also contains microtubules, which are long, hollow
tubes used for structure inside eukaryotic cells without
a cell wall.
• Microtubules also transport substances from one part of cell to
another.
– In addition, the cytoplasm houses the organelles.
Organelles are structures within the cell that have
specific shapes and specialized functions.
• Organelles are found only eukaryotic cells.
• The nucleus is the organelle that contains DNA, the genetic
material of the cell.
• The nucleus contains the nucleolus. It is the site for rRNA
(ribosomal RNA) synthesis.
• The Endoplasmic Reticulum (ER) is the factory for protein
and lipid synthesis.
– Rough ER has ribosomes attached to the outside. It’s job is to
synthesize protein, (specifically proteins headed for the cell
membrane).
– Smooth ER has no ribosomes. It’s function is to synthesize
lipids.
• There are also free ribosomes, meaning that they
are not bound to the ER, in the cytoplasm. Free
ribosomes synthesize protein used inside cell.
• The Golgi Complex (or Golgi Apparatus) is the
post office for proteins. It packages and addresses
the proteins for their final destination inside the cell.
• The Mitochondria is the “power house” of the cell.
It is responsible for ATP synthesis.
– Aka. site of cellular respiration
– Other types of organelles that some cells have
are:
• Lysosomes, which store digestive enzymes that are
used by the cell to break down nutrients into units
small enough to be utilized by the cell.
• Vacuoles, which are temporary storage for proteins,
sugars, organic acids, and inorganic ions.
• Peroxisomes, which oxidize toxic substances into
hydrogen peroxide. They also contain the enzyme
catalase, that functions to safely decompose
hydrogen peroxide into substances that are not
harmful to the cell.
– Now complete the homework for Lecture #2. It
is due on Friday, September 8 at midnight.