Transcript Chapter 7 Presentation

Chapter 7: Cell Structure
Prokaryotic
http://ilovebacteria.com/bacterialcell.htm
Eukaryotic
http://classes.midlandstech.edu/carterp/Courses/bio225/chap04/ss6.htm
Cell Size
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Smallest living entity.
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Many different types:
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Simple bacteria
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Single celled organisms
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Complex organisms
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An important thing to note is that most bacteria are
10x smaller than common eukaryotic cells.
Microscopes
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Light Microscopes
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Use light to view
specimens
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Electron
Microscopes
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Use an electron
beam to create an
image on a screen.
Microscopes
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Advantages of light microscopes:
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Can easily view slide preps up to 1000x
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Can view living organisms
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Wide variety of uses
Disadvantages of light microscopes:
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Can only view slide preps up to 1000x
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Limitations in resolving power 0.2μm
“Fathers” of the Microscope
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Hans and Zacharias Janssen
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Self proclamation
Galileo
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Made a scope with 2 lenses, had a lot of
aberration.
“Fathers” of the Microscope
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Antoine van Leeuwenhoek
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Considered the father of the scope, but actually did
so with many other people. Was selfish. His
scopes were giant lenses ~266x
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Very detailed specimens, brought microscopy to
forefront of biology.
Christian Huygans
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Corrected for chromatic aberration
“Cell”
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Who actually saw the “first” cell is in dispute, but
suffice it to say that it was probably some time in the
mid 1600s.
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In 1665, Robert Hooke built a microscope and
looked at thin slices of cork.
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He coined the term “cell.”
Cell Theory 1839 - present
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Matthias Schleidan and Theodor Schwaan and Rudolf
Virchow
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Cells are fundamental units of all living things
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Living organisms consist of one or more cells
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All cells arise from pre-existing cells
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Genetic material is passed from one cell to the
next during division
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All cells are essentially the same chemically
Spontaneous Generation
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Most people believed this was the way in which
organisms arose.
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Worms from meat
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Beetles from dirt
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Rodents from grain
A number of experiments were going on at the time
that didn’t support this, but many people still
believed in it.
Experiments against
Spontaneous Generation
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Francesco Redi
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Experiment using rotten
meat
Lorenzo Spallanzani
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Boiled broth and sealed it
shut showing no growth
Images taken from Microbiology Principles and Practices, Jackie Black.
Louis Pasteur
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Helped lend credence to cell theory.
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Disproved the notion of spontaneous generation
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Used “swan necked” flasks to trap microorganisms
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Poured the broth to mix in with the trapped
microorganisms and got bacterial growth
Louis Pasteur
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Disproved the notion of
spontaneous generation
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Used “swan necked” flasks
to trap microorganisms
Images taken from Microbiology Principles and Practices, Jackie Black.
Two Main Types of Cells:
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Prokaryotes
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Eukaryotes
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Kingdom Eubacteria
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Kingdom Eukarya
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Kingdom Archea
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Contain no membrane
bound nucleus or
organelles
Contain a membrane
bound nucleus and other
organelles.
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About 10x larger than
prokaryotes.
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About 10x smaller than
typical eukaryotes
Similarities between
Prokaryotes & Eukaryotes
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1. They are bound by a plasma membrane
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2. They contain cellular fluid called cytoplasm
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3. They contain chromosomes
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4. They contain ribosomes (although they are
different)
Cell Size Limitations
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Cell size is limited by the surface area to volume
ratio. As the cell becomes larger, this ratio becomes
smaller and it becomes more difficult for the cell to
adequately perform its functions.
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Recall the importance of a cell’s surface in allowing
things in and out of the cell.
Organelles
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Recall that organelles are found in eukaryotic cells
and perform various functions.
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Many similarities, some differences:
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*Animal cells contain lysosomes, centrioles and
flagella, plants don’t.
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*Plant cells have a cell wall, central vacuole and a
tonoplast, animals don’t.
Nucleus
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Control center of a cell, contains DNA in the form of
chromosomes.
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Chromatin-DNA/protein complex
Surrounded by nuclear envelope--regulates entry
and exit of macromolecules.
Nucleolus (“little nucleus”)
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Contains rRNA
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Makes ribosomes which end up on the cytoplasm
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Ribosome “factories”
The Nucleus
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Within the nucleus
are the chromosomes
and one or more
nucleoli which
function in ribosome
synthesis.
Ribosomes
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Found in both prokaryotes and eukaryotes
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They synthesize proteins by using the mRNA to
produce the 1° structure of the protein.
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Found freely in the cytoplasm and also are found
attached to the ER or nuclear envelope.
Ribosomes
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Free ribosomes:
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Make proteins for use
within the cell
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Bound Ribosomes:
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Make proteins which
are inserted into
membranes,
packaging within
certain organelles, or
to be exported from
the cell.
Endomembrane System
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Membrane system found within the cell and carries
out a variety of functions:
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Synthesis and transport of proteins
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Detoxification and movement of intracellular
products.
Endoplasmic Reticulum
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The ER is an extensive network of membranous
tubules and sacs (cisternae).
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The ER is continuous with the nuclear envelope.
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It has a membrane that separates the lumen from
the cytosol.
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There are two types:
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Rough endoplasmic reticulum (RER)
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Smooth endoplasmic reticulum (SER)
Endoplasmic Reticulum
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RER is studded with
ribosomes.
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SER is not.
Two types of ER
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RER:
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Studded with
ribosomes
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Proteins made go to
the lumen where they
take on their 3°
structure.
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Secretory proteins,
wrapped in a
membrane bound
vesicle to be shipped
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SER:
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Involved in the
synthesis of lipids,
phospholipids and
steroids.
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Detoxify drugs and
poisons, assist in
removal from the
body.
Golgi Apparatus
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Shipping and receiving center of the cell.
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After leaving the ER, products are dumped into the
Golgi at the cis face (closest to the ER). Here they
are sometimes modified and then head to the trans
side of the Golgi.
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These products then bud off from the trans face of
the Golgi and head to their destination.
Lysosomes
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Membrane bound organelle that stores hydrolytic
enzymes that break down macromolecules.
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They also do clean up functions within the cell.
Vacuoles
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Found in plant cells
and store a variety of
compounds, both
good and bad.
(Nutrients and
poisons).
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It isolates the
cytoplasm of the plant
cell from the water,
food, or other things.
Mitochondria
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Sites of cellular respiration that generate ATP for a
cell.
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Have an inner and an outer membrane.
Mitochondria
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Outer membrane:
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Inner membrane:
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Smooth and
surrounds the entire
mitochondria.
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Has many foldings
called cristae which
increases the surface
area of the organelle.
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Good for a lot of
cellular respiration.
Chloroplasts
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Sites of photosynthesis found in plants and algae.
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Have an inner and an outer membrane.
Chloroplasts
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Outer membrane:
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Houses all of the
structures of the
chloroplast.
Inner membrane:
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Contains a membranous
system of thylakoids,
grana, and stroma.
Images taken from Microbiology Principles and Practices, Jackie Black.
Chloroplasts, Inner Membrane
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Thylakoid: often found in stacks like poker chips.
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Each stack is called a granum.
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These are the sites of the light reactions.
These reside in the stroma--the liquid inside the
chloroplast.
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The stroma is the site of the dark reactions (Calvin
cycle).
Chloroplast and Peroxisome
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Peroxisomes contain catalase and are involved in
breaking down H2O2--a toxic compound formed as a
normal part of cellular metabolism.
Mitochondria and
Chloroplasts
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Not part of the endomembrane system.
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They have their own DNA which synthesizes
proteins on their own ribosomes.
Peroxisomes
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Membrane bound and add H+ from certain
substrates to O- creating H2O2 (hence the name).
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Peroxisomes have two main jobs:
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Create products that can be used by cellular
respiration.
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Detoxify.
The cell contains enzymes that break down H2O2
into H2O and O2.
The Cytoplasm
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It is a fibrous network of microtubules,
microfilaments and intermediate fibers (called the
cytoskeleton).
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Provides structural support, (no cell walls)
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Serves as an anchor point for organelles.
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Allows substances to be transported throughout the
cell.
Cytoskeleton
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A TEM of the
cytoskeleton.
Microtubules and
microfilaments are
evident, intermediate
filaments are not.
Microtubules
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Provide structural support
for the cell.
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Serve as transport tracks
along which many products
move as they transfer to
the plasma membrane for
discharge from the cell.
(neurotransmitters, etc.)
Microtubules
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Microtubules make up
cilia and flagella in
eukaryotes.
Microfilaments
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Smallest fibers and built from actin protein.
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Provide structural support and are involved in
motility.
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Work closely with myosin in muscle cells allowing it
to contract.
A Structural Role of
Microfilaments
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The surface of this nutrientabsorbing intestinal cell is
increased by its many
microvilli, cellular extensions
reinforced by bundles of
microfilaments. These actin
filaments are anchored to a
network of intermediate
filaments.
Microfilaments and Motility
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Microfilaments are involved
in muscle contraction,
amoeboid movement and
the streaming of particles
within the cytoplasm of plant
cells.
Intermediate Filaments
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Provide permanent structural support for the cell.
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Microtubules and microfilaments are often broken
down and built back up when and where needed.
Intermediate filaments are not.
Plant Cells
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Contain a cell wall.
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Provides support for the plant.
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Young plants secrete a primary cell wall rich in
polysaccharide. Glues the cells together.
Animal Cells
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No cell wall. Do have an extracellular matrix
composed of glycoproteins (collagen) and
proteoglycans (found in cartilage).
Levels of Organization
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Cells are organized in many organisms to form
tissues--cells that have similar structures and
functions.
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Tissues are arranged into organs--a structure with a
particular function.
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Organ systems are a group of organs that carry out
major body functions.