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THE CELL
CELL THEORY,STRUCTURE AND FUNCTION
Discovery of the Cell
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The invention of the microscope
made the discovery of the cell
possible.
1665: Robert Hooke used an early
compound microscope to observe a
thin piece of cork (plant material). He
observed empty chambers, which he
called “cells.”
1677: Anton van Leeuwenhoek used a
single lens microscope to observe pond
water. He saw tons of microorganisms
(bacteria, protists), even in the water he
drank!
Discovery of the Cell
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1838: Schleiden concluded that plants are made of cells.
1839: Schwann concluded that animals are made of cells.
1858: Virchow concluded that new cells came only from
other living cells.
Discovery of the Cell
These discoveries were confirmed by other
scientists & are summarized in the CELL
THEORY:
1. All living things are made of one or
more cells.
2. Cells are the basic units of structure &
function in living things.
3. New cells are produced from existing
cells.
Prokaryotes & Eukaryotes
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While all cells share 3 characteristics,
• Surrounded by a cell membrane
• Contain genetic material (DNA)
• Have ribosomes
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They are divided into 2 broad
categories:
1. Prokaryotic Cells (prokaryotes)
2. Eukaryotic Cells (eukaryotes)
Prokaryotes & Eukaryotes
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Prokaryotic Cells (prokaryotes)
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Do not have a nucleus or any membranebound organelles
Average Size: 1 micrometer
Example: bacterial cells
Prokaryotes & Eukaryotes
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Eukaryotic Cells (eukaryotes)
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Have a nucleus and membrane-bound
organelles
Average size: 10-100 micrometers
Example: animal & plant cells, amoeba
Prokaryotes & Eukaryotes
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Both prokaryotes & eukaryotes…
• …have cell membranes.
• …contain chromatin (condensed
DNA).
• …contain ribosomes.
Prokaryotes & Eukaryotes
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Both prokaryotes & eukaryotes have cell membranes:
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Function of the cell membrane:
• Protective barrier from the outside environment
• Controls what goes in and comes out of the cell
“selective permeability”
Prokaryotes & Eukaryotes
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Both prokaryotes & eukaryotes have cell
membranes:
Structure of the cell membrane:
• Phospholipid bilayer
• Proteins & cholesterol in it
Prokaryotes & Eukaryotes
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Both prokaryotes & eukaryotes contain chromatin:
chromatin
Prokaryotes & Eukaryotes
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Both prokaryotes & eukaryotes contain ribosomes:
PART II CELL STRUCTURE
What membrane-bound organelles
characterize the eukaryotic cell?
What is the function of these
organelles, and what relationships
exist between their form & function?
Cytoplasm
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Structure:
• Thick, watery substance (cytosol)
• All the cellular contents between the plasma
membrane and nucleus
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Function:
• Contains all the
organelles
• Where most
chemical reactions
occur
Eukaryotic Cell Structure
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Organelles are specialized structures
that perform specific functions vital
to the life of a cell.
Cellular organelles can be thought of
as little organs.
Just as organs function to keep the
body alive, organelles perform the
functions of the cell.
Nucleus
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Structure:
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Bound by a nuclear membrane
Location of chromatin (DNA) which holds all
instructions for making proteins
Nucleolus = region of highly condensed DNA,
where ribosomes are made.
Function:
•
Control center of
the cell
Ribosomes
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Structure:
• Small particles of RNA and protein
• Found floating in the cytoplasm or attached
to the rough endoplasmic reticulum
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Function:
• Make proteins (protein “orders” from the
nucleus)
Endoplasmic Reticulum (ER)
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Structure:
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System of membrane channels
Rough ER (studded with ribosomes)
Smooth ER
Function:
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Channels serve as paths for the synthesis
& transport of materials through & out of
the cell
• Chemical reactions occur on the
membranes
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Rough ER: site of protein synthesis
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Smooth ER: site of lipid synthesis
Endoplasmic Reticulum (ER)
Endoplasmic Reticulum (ER)
Golgi Complex
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Structure:
• Stack of flat membranes
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Function:
• “Post office” of the cell
• Modifies, sorts, packages, &
ships proteins
• Products received from ER
are modified, tagged, & sent
through & out of the cell
• Produces vesicles used for
transport throughout cell
Golgi Complex
Lysosomes
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Structure:
• membrane-bound sacs
• filled with enzymes
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Function:
• Enzymes break down carbs, lipids, &
proteins into smaller pieces
• Break down old organelles
• Where harmful foreign materials
can be destroyed
• Basically get rid of the junk
Vacuoles
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Structure:
• In plants, there is one
large central vacuole
• Membrane-bound sac
Function:
• Stores water, salts, proteins, carbs
• Plants: maintains rigidity (turgor
pressure)
• Unicellular: contractile vacuole used to
pump excess water out of the cell
• Maintaining water content is part of
homeostasis
Large Central Vacuole
Mitochondria
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Structure:
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Double layer membrane
Inner membrane has lots of folds which
increases surface area
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Function:
Mitochondria
• “Powerhouse” of the eukaryotic cell
• Where glucose is broken down in order to
produce useable energy for your body (ATP)
C6H12O6 + 6 O2 --> 6H2O + 6CO2 +
energy
exothermic or endothermic reaction?
Mitochondria
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Interesting Fact:
• Mitochondria are only passed down to
offspring by women (men do not pass
down mitochondria)
• So your mitochondria in your cells all
came from your mom!
Another interesting fact:
• The DNA in your mitochondria is
different from the DNA in your
chromosomes. Your mitochondrial
DNA also came from your mother.
Chloroplast
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Structure:
• Surrounded by a double membrane
• Inside, stacks of membranes (grana) -> increased surface area
• Where chlorophyll is stored
Chloroplast
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Function:
•
Site of photosynthesis: where energy
from sun is captured & converted into
chemical energy (glucose)
6CO2 + 6H2O + sunlight  C6H12O6 + 6O2
exothermic or endothermic reaction?
Cytoskeleton
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Structure:
• Made of microtubules (tubulin),
intermediate filaments, microfilaments
(actin)
Cytoskeleton
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Function:
• Gives shape and
organization to the
cell.
• Aids in cell movement
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Assembly of actin
Cilia/flagella
• Involved in cell division
(centrioles)
Cilia and Flagella
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Organelles with the capacity for movement
Extend from surface of the cell
Centrioles
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Structure:
• Pair of microtubule bundles
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Function:
• Used in cellular division in ANIMAL
cells
• Not present in plant cells
Cell Wall
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Made of cellulose
• What kind of molecule is cellulose?
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Provides plant cells w/ more rigidity
than animal cells
Plant vs. Animal Cells
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Create a Venn Diagram to compare
and contrast the structure of plant
and animal cells.