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THE DISCOVERY OF THE CELL
• It was not until the mid-1600’s
that scientists began to use
microscopes to observe cells.
• In 1665, Englishman Robert
Hooke used an early compound
microscope to look at a slice of
cork, plant material.
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CORK CELLS
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• Hooke saw thousands of empty chambers
which he called cells. They reminded him
of a monastery’s tiny rooms, which were
called cells.
• In Holland around the same time, Anton
van Leeuwenhoek used a single-lens
microscope to observe pond water and
other things.
• He discovered that living things seemed to
be everywhere, even in the water he was
drinking.
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Paramecium
Spirogyra
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THE CELL THEORY
• In 1838, German botanist
Matthias Schleiden concluded
that all plants were made of cells.
• In 1839, German biologist
Theodor Schwann stated that all
animals were made of cells.
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• In 1855, German physician
Rudolf Virchow concluded that
new cells could be produced only
from the division of existing cells.
• These discoveries, confirmed by
other biologist, are summarized
in the cell theory.
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• CELL THEORY STATES…
1. All living things are composed of
cells.
2. Cells are the basic units of
structure and function in living
things.
3. New cells are produced from
existing cells.
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THE CHANGE OF THE
MICROSCOPE
• Hooke, Virchow, and others
used crude microscopes to study
the cells.
• Today scientist can use a variety
of different techniques.
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• High resolution video to make
movies of cells as they grow.
• Transmission electron
microscope
–electrons pass through thin slices of
cell parts
–Cells must be dead and in a
vacuum
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CONFOCAL
LIGHT
TEM
TEM
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CHLOROPLAST
• Scanning electron microscope
–produces three-dimensional images
of cells
–Do not have to cut cells into slices
–Vacuum
TEM is more powerful than SEM
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MARINE DIATOM
SEM
SCANNIING
ELECTRON
MICROSCOPE
pea weevil egg
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White pine sheath mite
on eastern white pine
Scanning electron microscope
image of white pine sheath mite
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Sheet metal as seen with an SEM
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PROKARYOTES and
EUKARYOTES
• Cells fall into two categories,
depending on whether they
contain a nucleus.
1. Eukaryotes (YOUkaryotes)have a nucleus.
2. Prokaryotes (Pro=NO)no nucleus.
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PROKARYOTIC CHARACTERISTICS
• Smaller than eukaryotic cells
• Genetic information is not contained by a
nuclear membrane
• NO internal membranes
• Less complex compared to eukaryotic
cells
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• Some glide and swim through
liquids.
• Forms of locomotion are:
• Cilia – hair like structures
• Flagella – whip like structure.
------Example of Prokaryotes: Bacteria
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EUKARYOTIC CHARACTERISTICS
• Larger than prokaryotes
• They usually contain dozens of structures
and internal membranes = organelles
• Genetic info is carried by a nucleus.
• Some live solitary lives while other form
large multicellular organisms.
• Examples: plants, animals, fungi, and
protist.
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PARTS OF THE CELL
• Cell biologists divide eukaryotic cell into
two parts: the nucleus and the
cytoplasm.
• The cytoplasm is the portion of the cell
that is outside the nucleus. (includes
the organelles)
• Cytosol = is the internal fluid of the
cell, and a large part of cell metabolism
occurs here
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THE NUCLEUS
• The nucleus is the control center
of the cell.
• It contains the cell’s DNA and the
code for making proteins and
other important molecules.
• The nucleus is surrounded by a
nuclear envelope composed of
two membranes.
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• The envelope is dotted with
thousands of pores, which allow
materials to leave the nucleus to
other parts of the cell.
• Inside of the nucleus is a granular
material called chromatin.
• Chromatin consists of DNA
bound to protein (histones).
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Structure of DNA
• http://www.johnkyrk.com/chromosomestru
cture.html
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• When a cell divides, the
chromatin condenses to form
chromosomes.
• These are the distinct structures
that are passed from cell to
cell…generation to generation.
• Deep inside the nucleus is the
nucleolus which is where
assembly of ribosomes begins.
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? QUESTION ?
• WHAT KIND OF INFORMATION IS
CONTAINED IN CHROMOSOMES ?
• ANSWER: Genetic Information known
as DNA
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RIBOSOMES
• One of the most important jobs
carried out in the cell is making
proteins.
• Proteins are assembled in
ribosomes.
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• Ribosomes are small particles of
RNA and protein found
throughout the cell (mostly
cytoplasm).
• Ribosomes produce proteins by
following coded instructions that
come from the nucleus.
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? QUESTION ?
• WHAT DO RIBOSOMES
PRODUCE ?
• ANSWER: PROTEINS
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ENDOPLASMIC RETICULUM
• The endoplasmic reticulum also
known as ER. It is the site where
lipid components of the cell
membrane are assembled, along
with proteins and other materials.
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• The portion of the ER involved in
synthesis of proteins is called
Rough ER.
• Rough ER = ribosomes found on
the surface.
• Newly made proteins leave
ribosomes and are inserted into
the Rough ER, where they can be
chemically modified.
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• There are other portions of the
ER called Smooth ER because
no ribosomes are embedded.
• Smooth ER contains enzymes
that synthesize lipids and the
detoxification of drugs. (liver cells
contain a lot of Smooth ER)
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? QUESTION ?
• WHAT IS THE ROLE OF THE
Rough ER ?
• ANSWER: to synthesize proteins
& chemically modify them
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GOLGI APPARATUS
• The Golgi Apparatus receives
proteins from the Rough ER.
• The job of the Golgi Apparatus is
to modify, sort, and package
proteins for storage or secretion
outside the cell.
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• The Golgi Apparatus is like a
customizing shop that puts on the
final touches before proteins are
shipped out.
• It is also like the UPS of the cell.
It doesn’t make anything, but it
sorts and packages items.
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Golgi Animation
• http://www.johnkyrk.com/golgiAlone.html
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? QUESTION ?
• WHAT IS THE ROLE OF THE
GOLGI APPARATUS ?
• ANSWER: It modifies, sorts, and
packages proteins, lipids, and
other materials/chemicals.
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VACUOLES
• Vacuoles are saclike structures that
store materials such as water, salts,
proteins, and carbohydrates in all
organisms.
• Plant cells have vacuoles. They help
each cell maintain water pressure to
hold up heavy structures such as
leaves and flowers.
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• Some single-celled organisms &
plants have contractile vacuoles
which regulates the water inside
the cell.
• Contractile vacuoles help cells
maintain Homeostasis or “internal
balance”
• Central Vacuole = holds water
and waste materials for plants
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? QUESTION ?
• WHAT IS THE ROLE OF A
VACUOLE ?
• ANSWER: They store materials
and help plants maintain their
structure
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LYSOSOMES
• Lysosomes are the clean up
crew of the cell.
• They are small organelles filled
with enzymes that break down
and digest lipids, carbohydrates,
and proteins.
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? QUESTION ?
• WHAT IS THE ROLE OF THE
LYSOSOME ?
• ANSWER: clean up the cell and
get rid of material & breaks down
lipids, carbohydrates, and
proteins
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CELLS AND THEIR POWER
• Nearly all eukaryotic cells,
including plants contain
Mitochondria.
• Mitochondria are organelles that
convert the chemical energy
stored in food into compounds
that are more convenient.
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• In humans, all or nearly all our
mitochondria come from the
cytoplasm of the ovum, or egg
cell.
• In plants, chloroplasts are the
organelles that capture the
energy from the sunlight and
convert it into chemical energy in
a process called photosynthesis.
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• Both mitochondria and
chloroplast are the only
organelles that have small DNA
molecules.
• Scientist have evidence that these
two organelles may have been
descendants of ancient
prokaryotes at one time.
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CYTOSKELETON
• The cytoskeleton is a network of
protein filaments that help the cell
maintain its shape.
• Microfilaments and Microtubules
make up the cytoskeleton.
• Microfilaments are threadlike made
of a protein called actin.
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• Microtubules are hollow
structures that are made up of
proteins called tubulins.
• In animal cells, tubulin helps in
the development of centrioles.
• Centrioles are located near the
nucleus and help in cell division.
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• Cell membrane = phospholipid
double layer with protein,
carbohydrates, and other
molecules embedded.
• Cell wall (plants, fungus, and
some protists) = tough outer
covering
–Plants – made of cellulose
–Fungus – made of chitin
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